This is a continuous glucose monitor (CGM) made by Dexcom, Inc. Dexcom web site.
The Dexcom CGM gets a glucose reading every five minutes, about 288 readings every day. In addition it will collect event markers for things like exercise, carbs consumed, and other data. It also collects calibration results, generally two of these each day.
Currently there are two versions of the Dexcom software, which can be installed at the same time on a single PC: DM2, and DM3.
You can export data from the Dexcom DM3 by following these steps.
I've loaded a copy of the XML format file, and the Tab Delimited Text file to this wiki.
Update September 17, 2012: I started using version 12.0.2.25 of the Dexcom studio software. I've exported more data in case the data formats have changed: newer Tab Delimited Text file; newer XML format file.