From
http://www.getinpulse.com/faq/I've ported DOOM (or another cpu-intensive application) to the watch, but now I can't connect by bluetooth!
If an application is doing a lot of processing, bluetooth may become inactive. You can get in to the backup firmware image by holding the button for about 20 seconds until you see "Loading..." on the screen. Then you will be able to upload firmware and/or resources again.