The Socialable Geek, Daniel Egan, has posted his seventh episode of the WP7 Minute and this one highlights some handy diagnostics on your Windows Phone 7.
Episode 7 – Cool Diagnostics – In this episode, we look at the cool ## diagnostics menu. A cool hidden menu for the WP7 Samsung
I tried this on my LG Quantum and it did not work so this is not universal to all handsets. I imagine different manufacturers – different methods.