The Rev 2 Pi has a reset connection that will restart the Pi after it has been halted.
Look for the two pin connector P6 - between the HDMI connector and the large aluminium capacitor. Unfortunately it doesn't have any pins installed but if you short the two connections together this will reset the Pi and it will power up as normal. It's on page one of the schematic for the Pi. http://www.raspberrypi.org/wp-content/u ... .2_027.pdf
You could solder in two pins and plug on a switch with a cable and two pin connector. Then just push the switch to restart the Pi.
But be careful not to push it while it is on. Depending on what the Pi is doing you might possibly corrupt the SD card by resetting the Pi at the wrong time.
Simplicity is a prerequisite for reliability. Edsger W. Dijkstra
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