In some code I'm writing for GAE I need to periodically perform a GET on a URL on another system, in essence 'pinging' it and I'm not terribly concerned if the request fails, times out or succeeds.

As I basically want to 'fire and forget' and not slow down my own code by waiting for the request, I'm using an asynchronous urlfetch, and not calling get_result().

In my log I get a warning:

Found 1 RPC request(s) without matching response (presumably due to timeouts or other errors)

Am I missing an obviously better way to do this? A Task Queue or Deferred Task seems (to me) like overkill in this instance.

Any input would appreciated.

A task queue task is your best option here. The message you're seeing in the log indicates that the request is waiting for your URLFetch to complete before returning, so this doesn't help. You say a task is 'overkill', but really, they're very lightweight, and definitely the best way to do this. Deferred will even allow you to just defer the fetch call directly, rather than having to write a function to call.