Dash, makers of the Dash Express GPS unit, recently opened up their API so that developers could create applications taking advantage of the device's GPS and cellular network connection. One of the newest additions to the Dash software catalogue has been Dave Zatz's Twitter app, which not only allows you to download the latest 20 posts from your friends' but to auto-compose messages containing anything from personal text and your address, street, city, state, latitude or longitude, to links to Yahoo! or Google mapping.
Check out the videos of the Dash Express Twitter app after the cut
There's no PC required to relay the message, it's all done via the Dash Express' network connection. Right now it's set to send only when instructed - in the video, Dave Twitters his location outside a Krispy Kreme donut shop, and a link to Google Maps is automatically added to the message - but you could feasibly have it poll Twitter regularly and run some sort of real-time geoblog.
The Twitter app is available from DashApps.net now. There are also programmes to let you look for housing, check rental rates for the area you're currently driving in, and even one that alerts you to what interesting things are happening nearby (if you're indecisive).