This article from MIT has lots of good information about power scavenging, including a survey of piezo buttons, one of which powers up a transmitter and sends data. This would make a nice aiosphere device, I think: a button you can stick anywhere in your house, and it does whatever you want it to. Maybe you can label it? True to the principle of the aiosphere, the button doesn’t need to be programmed, or have any ‘understanding’ of its purpose: that is all established by the server, or the receiving device.
Maybe a super-fancy version uses e-ink to label itself (zero static power).