You know that HRV is a reliable index of autonomic nervous system regulation. You know polyvagal theory. You know that resonance frequency breathing improves vagal tone and that vagal tone predicts emotional regulation capacity. You may use biofeedback equipment in your practice already, or you may have read about it and found the real-world delivery gap too large to bridge with the families you see.
That gap is what Keel is designed to close.
This letter is not a pitch. It is a clinical briefing. We want you to understand exactly what Keel does, what it does not do, how it relates to your existing treatment framework, and what the data your clients generate looks like. We want you to be able to make an informed decision about whether Keel is something you would recommend to a family, knowing that your recommendation carries professional weight and that we take that seriously.
Keel does not replace what you do. It operates in the 166 hours per week when your client is not with you.
The delivery gap in pediatric HRV biofeedback
The evidence base for HRV biofeedback in children and adolescents is substantial and growing. A 2021 systematic review in the Journal of Child Psychology and Psychiatry covering all published human studies found that HRV biofeedback sessions with children and adolescents efficiently reduced physical and mental health-related symptoms and improved wellbeing across anxiety, stress, pain, and ADHD presentations. The reviewers specifically highlighted its value as a complement to cognitive and behavioral interventions.
The consistent limitation across the research is the delivery model. Studies use clinic-based equipment, trained practitioners present during sessions, and structured protocols that require the child to sit still and consciously engage with the biofeedback process. Compliance at home with traditional equipment is poor. The gap between what works in a controlled research setting and what a family can sustain between sessions is significant.
This is not a minor implementation detail. It fundamentally limits the therapeutic value of a technique that works precisely because it builds vagal tone over time through repeated practice. A child who does five sessions in your office and no practice at home is unlikely to show the baseline HRV improvements that translate to real-world regulation gains.
Keel delivers the physiological intervention passively. The child does not need to remember to practice. Practice happens whether or not the child chooses it.
What Keel does mechanically
Keel uses Apple Watch HealthKit to monitor HRV and heart rate continuously against each child's individual contextual baseline, established over a 7-day passive calibration period. The baseline is time-of-day specific: after-school HRV is benchmarked separately from morning resting HRV, which is benchmarked separately from weekend patterns. This matters clinically because contextual baseline variation is large in children and population averages are not useful.
When HRV begins dropping and heart rate begins climbing without movement explanation, the watch initiates a continuous haptic wave on the wrist. The wave intensity and rhythm are calibrated to the child's resonance frequency breathing cadence — approximately 3.5-second cycles for younger children and 5-second cycles for older children, based on the established difference in pediatric versus adult resonance frequency ranges. The haptic pattern uses CoreHaptics with low sharpness throughout. The sensation is rounded and rhythmic rather than sharp or alarming.
The child does not need to consciously engage. The nervous system can entrain to the rhythm before the prefrontal cortex has processed that an alert is occurring. When the child opens the breathing tool actively, the haptic becomes a direct breathing guide: intensity rising on inhale, fading on exhale, usable with eyes closed in any environment.
Red zone events require biometric confirmation to close, not self-report. HRV must return to within 15% of contextual baseline before the system registers recovery. This prevents the common pattern of behavioral compliance masking continued physiological dysregulation, which you will recognize from clinical practice.
The data your client generates
Every Keel session produces structured episode data that is directly relevant to clinical work. The therapist export includes:
- Episode log — timestamp of HRV deviation onset, timestamp of behavioral expression if reported by parent, duration of Red zone, recovery time to baseline.
- Morning HRV trend — daily baseline scores against 7-day rolling average, flagging days when the nervous system began the day already depleted.
- Recovery window — each child's personal average recovery time from Red zone entry to biometric confirmation, tracked weekly.
- Intervention response — whether the breathing tool was used, how many cycles, and whether HRV recovery correlated with tool use.
- Weekly regulation score — frequency and duration of Yellow and Red zone events over time, showing trend direction.
This data addresses something you likely encounter regularly: the difficulty of tracking autonomic regulation progress between sessions using behavioral report alone. A parent's account of how the week went is filtered through their own stress level, recency bias, and the cognitive load of managing a dysregulated child. The Keel export is objective, timestamped, and physiologically grounded.
A child showing shortening recovery windows over 8 weeks has a measurably more regulated nervous system regardless of what the parent's narrative says.
For psychotherapists
Keel does not deliver any therapeutic content. It does not offer CBT tools, narrative techniques, or emotion-labeling frameworks. What it does is improve the physiological conditions under which those techniques work.
A child arriving at your session after a school day in which their autonomic nervous system has been repeatedly activated and is running depleted is a child with a prefrontal cortex that is less available for the reflective, language-mediated work of therapy. Higher baseline vagal tone means a wider window for cognitive engagement. Research on the integration of biofeedback with psychotherapy consistently finds that physiological regulation support enhances therapeutic outcomes, particularly for children with anxiety, ADHD, and trauma presentations.
The episode data from Keel can inform session content directly. A child who has had three Red zone events in the three days before a session has concrete, physiologically documented material to work with. The timing data shows what precedes escalation. The recovery data shows what the nervous system responds to. That is richer clinical context than a weekly verbal check-in.
For occupational therapists
The interoception angle is where Keel is most directly aligned with OT practice. Kelly Mahler's interoception curriculum, widely used in OT with autistic and sensory-processing children, builds the same capacity Keel is providing an external scaffold for: awareness of internal body states as the foundation of emotional self-regulation.
Keel's haptic wave functions as an externalized interoceptive signal. For a child whose proprioceptive and interoceptive systems are not reliably generating the internal warning signal of escalation, the watch provides an external physical reference point at the moment the autonomic shift is measurable. Over repeated associations between the haptic signal and the internal state, research on interoceptive training suggests this external reference can support development of internal awareness. The watch can be understood as a prosthetic interoceptive sense that fades as the child's own capacity develops.
The sensory design of the haptic is relevant to your practice. Intensity is kept low across all states. Sharpness is minimized throughout. The pattern is slow, rhythmic, and predictable. During onboarding there is an explicit sensory screening: any pattern the child finds aversive is disabled and visual-only alternatives are activated.
What Keel does not do
We want to be direct about scope because overclaiming is a failure mode we are actively trying to avoid.
- Keel is not a medical device and makes no diagnostic or treatment claims.
- Keel does not deliver therapeutic content of any kind.
- Keel does not replace professional clinical care. It is specifically designed as a between-session support layer.
- Keel does not generate clinical-grade physiological data. Apple Watch HRV uses optical photoplethysmography, not ECG. The data is reliable for trend detection and threshold monitoring, but is not equivalent to laboratory-grade HRV measurement.
- Keel does not make medication recommendations or provide clinical guidance of any kind.