BlueCore 4

The CSR BlueCore4-ROM WLCSP Chip (BC41B413A) is the Bluetooth chip used in the first generation iPhone.

Awesomely, this chip has an open datasheet

Hopefully the downloaded ROM supports the low level requirements for the other profiles. If not, downloading a replacement doesn't look too hard.

Stack
No detailed information so far.

However it is believed that out of a normal Bluetooth stack, all protocols up to but not including HCI are implemented on-chip in ROM. HCI and L2CAP seem to be handled (however badly) by the iPhone driver software.

Main article: Bluetooth