I have a Forerunner 405 and while it's a capable unit there's only so much that can be configured using the bezel and buttons.
Let's have a PC/Mac based settings manager. It doesn't have to be complicated and a single web page (part of MyGarmin or Garmin Connect?) should do it.
A button for 'retrieve device settings' and one to send ought to do it with a simple graphical (or text table maybe for starters?) display of all the various features.
I'm sure that most 405 (and other unit) users don't bother getting to half the settings - or leave them on (hint: beeping!) - as they can't fathom out the navigation and that's without mentioning the various issues people have with the bezel.
We already use ANT Agent to upload firmware, so presumably the radio supports two way communication.
Apologies if this does exist somewhere already and I haven't found it!