Privacy and security issues Owner-ship of user data. Users of consumer wearable devices today often do not own their data. Instead, the manufactur...

Restrictive OS-level APIs and Play Store policies that make it hard to collect GPS type of data. Require the development of in-house apps.

Wearables with GPS - although they allow the user to look at GPS information live, there is usually not a way to download a log of all GPS movements.

IMUs for actigraphy Compensation of noise sources due to quantization or arising from improper on-body unstable placement or misplacement and misal...

Validity and reliability of the measuring devices under free-living conditions Various wearable devices show large variations in accuracy between d...