Wearable experiment have produced a legging for Yoga participants that uses haptic feedback on the quality of your posture, when trying to achieve a particular position.
An Android app (and later IOS) lets you choose a position and gives localized feedback my vibrating small motors, probably similar to those in a smartphone. The sensing mechanism is not disclosed; speculating, it could use some form of stretch sensor, which would well suit a tight fitting garment such as a legging. Wireless charging is utilized to recharge the battery and the garment is washable, though after approximately 25 cycles the garment is likely to stop working and revert to a passive pair of leggings.
The original press release at CES talked about a release later in 2016, however I’ve not seen the garment for sale yet.
Source: Tech Insider