One thing that Windows Phones currently lack is a common API for accessing the compass feature, even though all phones require the hardware. As it turns out, some phones have easier access than others. My LG Quantum has the augmented reality app 'ScanSearch' which has a compass in it and evidently the Samsung Focus has driver support for a compass too.
Dave Amenta, responsible for Send to WP7 (Desktop) and Accent Changer has come through again with a compass app, albeit rudimentary, that totally works on the Samsung Focus (and presumably the Omnia 7). As of now, no support for HTC, LG or Dell, but that's probably just a matter of time anyways. We'll keep you posted.
As before, you'll need a developer unlocked device. Source code is available for developers too.
Read more here and thanks Dave for the heads up!