You mentioned body temperature twice, so I’m going to pick on that one. If it’s a wrist-based device, it’s going to measure your wrist temperature, which normally differs from your body temperature a great deal. The Oura ring works roughly the same with your finger.

What exactly are you looking for WRT your body temperature? Because for most fitness wearables, you just going to be able to log deltas. Kind of a solution looking for a problem at this point.

Overall, you should have well-defined goals before you purchase because a device that can log a bunch of body telemetry gets boring pretty quickly without solid goals.