I may be a bit late, but here is an app that I wrote that does what you want:
http://niltz.github.com/projects/mytrax.html
It creates a gpx file with timestamps, and can be accessed via iTunes:
- open iTunes
- choose your device
- select the "Apps" tab
- under "File Sharing" locate MyTrax
- you can then access all of the exported gpx file and save them to your computer (and delete them from your device if you want)