Hello!
I have been thinking about making a datalogger for mobile use and cables/interference have been most problematic issue.
Now when Symbian series-60 phones with BT are affordable at low prices (n-gage 100e), this issue could be solved nicely with BT. Phone could be used as datacollector (to MMC) and/or realtime viewer.
How to connect microcontroller @ low cost to bluetooth? RS232 (or just serial) to BT conversion should be bullseye solution to this, but ready made boxes aren't too cheap (200e).