The module has a rechargeable battery, which lasts for eight hours once charged.

CNN: Something clever up your sleeve

Inside, there's a replaceable CR2016 watch battery that's said to last more than a year, a Bluetooth module and antenna, an LED-lit ring and a piezoelectric speaker.

ENGADGET: StickNFind Bluetooth stickers let you tag and locate your goods with a smartphone (hands-on video)

Droplet is a compact self-contained module with an integrated RGB LED, a photodiode and a CR1216 lithium coin battery -- which provides roughly one day of power in the gadget's current early prototype status.

ENGADGET: Droplet and StackAR bring physical interface to virtual experiences, communicate through light (hands-on)