Wearable ring from Oura
"Oura developed a wellness ring that tracks and analyzes a user's rest and sleep. One of the differentiating features of the Oura ring, according to Wearable Technologies, is that the device does not need to transmit the data back to a mobile phone continually, but rather shares the data once it is within range of the smartphone."
Dawn, I feel this is quite good, simple and multifunctional. The need for all time connectivity can be minimized and hence data usage too.