Speedo Plus is a nice free app for Windows Phone 7 which lets you know how fast you are travelling using the GPS. This is handy when you are travelling by bus or a train and want to get the speed. Once the application is turned on, it gets you the speed in which you are travelling using the help of GPS.

Features;

• Supports both metric (km/h) and imperial (mph) measurements.
• Windscreen mode optimized for glass projection
• Charts speed over time
• Calculates moving average and maximum speed during trip
• Map underlay feature

Although the app has a trial version and paid version, the trial version has no limitations or trial period and it is fully functional.