It should be ok with 3.6V but battery reports may go crazy (showing over 100%). The ZSE40 is a 4-in-1 sensor so it reports temperature, humidity, and light levels next to motion.
We’ll be releasing 2 new motion sensors this year, one of them similar to the HomeSeer product but with more features. The other one will be a multisensor, similar to our ZSE40. Both will have the ability to accept USB power if this is something you’re looking for.