Similar to my previous app M25 for WP8, M1 allows you to monitor the current state of the M1 motorway here in the UK. Here's a few screenshots.
After publishing the M25 I stepped back and took a look at refactoring my codebase to support any motorway in the UK. As a result, the new version of M25 and the M1 app share a common core codebase. As well, the size of the xap file has gone down dramatically from about 500kb to around 275kb.
Anyway, if you are familiar with M25 you will know how to use the M1.
As always, comments/feedback/reviews are appreciated.