We found the other day that Apple and AT&T are not totally transparent regarding the true capabilities and compatibility status of the newly-released iPhone. It was found that owners can actually opt to go prepaid after tinkering with iTunes sign-up service and social security number.

Anyway, here's another "exploit" for all you iPhone freaks out there: removing the SIM that comes with the phone and/or putting in an inactive SIM will automatically convert your mobile phone into a a contract-free WiFi-enabled sixth generation iPod.

The key word there was WiFi as it allows you to do Mail and Safari without a phone connection. Pretty sneaky, eh? We thought so, too. In case you want to know how the trick is done, here's the test performed by the good guys of online blog TUAW:

• Removed SIM and replaced it with an invalid, unactivated, no-account SIM: Still works as 6G WiFi iPod. Still Synced properly to iTunes. Tried placing call. It failed (as expected).
• Removed SIM entirely: It complains but works at 6G WiFi iPod. Tried placing call. "No SIM card installed". Failed. Connected to iTunes. Synced without any problems I could detect. WiFi fine.
• Removed activated SIM and placed into a cheap disposable AT&T cell phone: Worked fine. Was able to place calls. Good way to save your iPhone from danger on ski or bike trips.
• Placed SIM from cheap disposable AT&T Pay as You Go phone into iPhone. Call failed. WiFi fine.