Do keypad commands come from Android or the manufacturer? I'm curious if keypad commands like those listed below come from the Android OS or if they're added by manufacturers. On my N1, I know of these two commands:

*#*#checkin#*#* - Phones home to check for updates.

*#*#info#*#* - Enters a detailed phone information menu.
There are many that seem to be "standard", but they can also be added by individual applications (e.g. provider-installed).

Check out http://forum.xda-developers.com/showthread.php?t=540483 for a method to extract telephony codes from your installed apps.