Seismo is another neat XDA Developers application that takes advantage of the G-Sensor in the HTC Touch Diamond and the HTC Touch Pro.
“Seismometers are instruments that measure and record motions of the ground, including those of seismic waves generated by earthquakes, nuclear explosions, and other seismic sources. Records of seismic waves allow seismologists to map the interior of the Earth, and locate and measure the size of these different sources.” (source: Wikipedia)
This application watches for any movement your device is involved in and translates it into an X/Y type graph, just like a regular Seismometer. In addition, you can use the Smart Touch wheel to zoom in the graphic thus offering you a more sensitive movement reading (I actually zommed in as far as I could and the application detected someone entering the room).
Install it to DEVICE and run from the Programs menu. Windows Mobile Professional required featuring .NET Compact Framework 3.5.