One thing that many Pocket PC and other Windows computers have is a Bluetooth interface. Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, PCs, printers, digital cameras, and video game consoles over a secure, globally unlicensed short-range radio frequency. The Bluetooth specifications are developed and licensed by the Bluetooth Special Interest Group.
OK, but I don’t see anything in this “official description” of Bluetooth that suggests that Bluetooth is good method to use for this simple – or for other even more complex – applications. And, by itself, that objection is correct. However, if we combine a simple microcontroller board that has a serial communications port, with a serial Bluetooth adapter, we now have a mechanism for sending and receiving wireless data between our Pocket PC or other computer and the microcontroller board. We can use the microcontroller to provide the interface to our sensors (anything from a simple switch to much more complex “stuff”) and also to provide a way for us to send commands and control signals from the computer to the microcontroller!
I think it's a subject you have to search about it... it will give you very good ideas