Forget fitness taker, smart watch and tiny little things. I'm thinking thin smartphones. If one of these can be powered by multiple RFID signal sources. Do the math for required power signal strength and get working around the limitations.
The arising bugs in most softwares I use daily seem like a result of features bloating. I post some idiosyncrasies i stumble on my twitter @shkesar feed as a reminder that I won't follow the same misdirected belief.
Couldn't they just use bluetooth to connect it with laptop keyboards. I'll use that. Most of the times I have my laptop open along with my tablet and phone.