title: Embedded Linux LED-flashing daemon: does it exist?
body: <p>I've seen embedded boards before that have an LED that flashes like a heartbeat to show that the board is still executing code. I'd like to do something similar on an embedded Linux board I'm working on. Given that it's a fairly trivial bit of code, it seems likely to me that someone has already written a daemon for Linux that does this, but I haven't been able to find any evidence.</p>
  
  <p>Note that OS X Server's heartbeatd and the High-Availability Linux <a href="http://linux-ha.org/wiki/Heartbeat" rel="nofollow">heartbeat daemon</a> are not what I'm looking for-- they both coordinate system availability over IP networks, or something like that.</p>
  
  <p>Assuming what I'm looking for doesn't exist, I'm also interested in advice about how to write a daemon that toggles a pin while minimizing resource usage. At what update rate does cron become a stupid idea?</p>
  
  <p>(I'd also rather not hear gushing about the LED on the sleeping MacBook Pro, if that seems relevant for some reason.)</p>
  
  <p>Thanks.</p>