Wrong lead-wrist angles you can't see or feel — cupping, over-flexing, casting and flipping — that destroy clubface control. The lead-wrist sensor (Sensor 4, 26 g) measures flexion/extension at address, top and impact, diagnoses the fault, and prescribes interactive drills with audio/vibration/visual feedback in the free HackMotion app.
✓Diagnoses 13 named full-swing faults (casting, cupped at top, overhinge, flipping at impact, and more)
✓Thin/fat shots, pushes/pulls and high/low ball flight caused by those faults (maker, fault-by-fault)
✓Progress tracking / regression detection and bookmarking best swings
Best for
Serious, practice-willing golfers who want measured clubface/wrist data and guided drills rather than a feel-only aid; golfers who slice, hook, push, pull or flip and don't know which wrist fault is causing it.
Not ideal for
Putting — Core license is full-swing only; Putting Mode is Plus/Pro (maker comparison). Not designed for tempo, swing speed or full-body motion (credible reviews). Golfers unwilling to use a phone app (inference). Rental ops: each unit needs a USB-C charge and Bluetooth/app-pairing test before shipping.
Skill level: Maker states no handicap range (target ranges adapt to the swing). Credible reviews say all handicap levels with mid-handicappers as the sweet spot; beginners may find it more technical (review-based, not a maker claim).
How it's used
Home, indoor simulator or driving range. Full-swing analysis requires hitting a ball at a range or simulator; in-app drills can be done without a ball. Right- and left-handed (select side in app); fits under/with a glove. $345 one-time, no subscription — Core/Plus/Pro are software licenses on the same sensor. Sensor 4: ~10 h battery, 2.5 h USB-C charge (maker specs).
You'll need:phone or tablet (iOS/Android) with the free HackMotion app (Bluetooth)USB-C charging cable (included in box)golf club(s)golf balls (for full-swing analysis at range/simulator)
