as discussed here :Features :- (Oct 2007)
Multiple cell phones can be connected (subject to some limitations - see Notes).
Multiple bluetooth adapters can be supported.
Asterisk automatically connects to each cell phone when it comes in range.
Command to discover bluetooth devices. Useful for configuration. Requires an unused bluetooth adapter.
Inbound calls to the cell phones are handled by Asterisk, just like inbound calls on a Zap channel.
CLI passed through on inbound calls.
Dial outbound on a cell phone using Dial(CELL/device/nnnnnnn) in the dialplan.
Use a Bluetooth Headset as extension using Dial(CELL/device) in the dialplan.
Application CellStatus can be used in the dialplan to see if a cell phone is connected.
Application MobileSMS to send SMS via a connected mobile phone
Supports devicestate for dialplan hinting.
http://bugs.digium.com/view.php?id=8919
http://www.voip-info.org/wiki/view/Asterisk+Bluetooth+channels