Nothing easier, solar powered with extra power outlet :) The above power consumption is zero, the solar would be negative (producing energy for the outside world instead of consuming :)

My personal ideas:
- standard '51 Emulator on a fast derivative. (software implementation of 8051 CPU in 8051 assembly)
- Interpreter chip (take some derivative with a lot of internal extras like an ADC, DAC, network, and drive all of them by sending commands over serial from the PC)
- SLIP router/switch/firewall on multi-RS232 derivative (IP stack implementation needed)
- NoTouch for manufacturers who don't provide it originally.
- Robotic arm
- Port Linux to '51 architecture (now THAT would be a feat!)
- MP3 audio casette: flash+MCU+DAC+tape recorder head+USB/RS232 interface for uploading songs, all enclosed in a standard tape recorder casette (with tape removed), insertable into any tape recorder, playing MP3 by emulating a real casette. Extra points for turning rotary motion of the mechanism into electricity to keep the device playing.
- Grey goo (a lot of small units communicating wirelessly and able to perform environment analysis just by getting scattered over the area, i.e. locate self by triangulation with other devices and then record route people walk by short-range motion detection and sharing the data over the network and performing distributed computations)