I was on the original Philips team that created the Bluetooth interface now used on most of the Compaq iPAQ models and lately the Dell Axim. My company has developed a C++ class library called BTAccess that allows programmers to get at all the underlying (Widcomm-based) bluetooth stack functions.
BTAccess works with all older models of the iPAQ, the Dell Axim, or any PocketPC PDA that uses the Philips/Widcomm (v1.2) CF card (branded as Philips, Dell, or Belkin). For the iPAQ 54xx, or any other PDA that uses the Widcomm v1.3 stack with PAN, use our BTAccess54 product.
For a complete functional eval kit (SDK, help file, sample source code) download the package at www.high-point.com. Also a great FAQ page about little-known or undocumented features.
President, High Point Software