I have a Brunton micro-traveller keychain compass that's similar to the Suunto Comet you suggested. I bought it from TAD Gear, but it's no longer on Brunton's website (I assume it's been discontinued). I don't normally carry it, but I can attach it to my chain easily when I want to. But I've always wondered if a compass on a keychain will stop working correctly after time. Sure, the included keyring is non-magnetic, but what about all of the other metal we carry on our keychain? Will this cause problems with the operation of the compass over time? And will the plastic around the lquid eventually break from all the beating it will take? What do you all think?