The Firefly is a Bluetooth class 1 Serial device with a db9 connector. It has 4 switches on the outside and 10 jumper pins on the inside for configuration. It can be connected to most serial devices and supports RX, TX, RTS, CTS, and GND. Power can come from the serial port, a standard wall adapter, or a usb port. It is available with a male or female DB9 connector.
The BluePort XP is very much like the Firefly but it has a rechargeable battery. You can get 24 to 30 hours of continuous connection and transfer of data on a single charge. It supports the same serial signals and is configured mostly the same way as the Firefly. Power can come from the internal battery, a wall supply, or a usb port. It is available with a male DB9 connector.
The BluePlug is also a class 1 bluetooth device which attaches to a host computers' USB port. It installs as a bluetooth device and usually installs automatically with Windows. There are drivers on the included CD that will install it as well. Since it needs drivers to run, it cannot be installed on devices that aren't computers or that don't have some means of installing software.
The FirePlug is like the BluePlug, however it installs as a serial port instead of a bluetooth device. It can also be set to pair with another bluetooth device, such as a Firefly or BluePort XP upon power up automatically. There are more features on the FirePlug product page.