Tough this is a great idea and I really would hate to get my N900 stolen or lost, don't you think this would be very complicated to use for noobs like me (ssh server and so on )

What about a new version of Nokias "5-Step-Plan" ?
Step 1:
A possibility to erase all private data from the device including SD-card by sending a data-package (Contacts, Conversations, Mailaccounts, Pictures, Docs...)
If the phone gets stolen, it is very likely that the Simcard will be changed by the bad guy, because locking the Sim takes at least a few minutes for each Provider - so there we need a solution for the case, that the bad mans Simcard includes no Dataplan
Step 2:
A possibility to totally brick the device by sending a data-package - if I can't use it, nobody else should
This would be fantastic with the option to unlock it again with a special code requested before booting (like bios-pw in Windows). There should also be no option to reflash the device with new firmware before entering the code....
Step 3+4+5: All mentioned above

To bad I have absolutely no idea of programming...

CU - M_99