Swoof 2000 Open
Sorta hacky but pretty cool –

The swooftronic 2000 is the original device in the swoof series. It is a very basic digital synthesizer that allows you to vary the upper pitch, lower pitch, note length, sweep rate, rest length and sweep length. Once you have set the desired value you press the play and the swoof loops through the sound over and over again.

The Swoof is controlled via the four button hand piece. The buttons allow you to move up and down through the menu system, enter and change new data and start play mode. There is also a load and save which allows you the keep and recall 10 sets of data, the data is stored even when the unit is not on and the battery is removed.

RareBeasts – Link.