I would search for Douglas Boling.  He wrote a Microsoft Press article on
Bluetooth and presented at the MEDC.  He provided sample code at the MEDC for
exactly what you are wanting.  I hope this helps.

Rick D.
Contractor

If you are using CF2 then it makes it easy for you to initiate a bluetooth
serial connection by using the SerialPort class.

Check out the previous posters suggestion also search for example on
SerialPort in CF, I'm sure you'll find lots of examples as this is a fairly
common requirement on mobile devices.