From what I have seen ( I could be wrong about thiss..) it would seem
that the typical os update functionality is something that is provided
by a boot loader. (drop an os upgrade on root of sd card, reboot into
special mode, and perform the upgrade).
Are companies building their own bootloaders,
There is a special boot mode known as recovery boot. which is implemented
by default in android. mydroid/bootable/recovery is the folder where you
will see the recovery related gui and you have some documentation in the
code. as of now most of them support entering into this mode using android
UI.
