Greg Surges’ USB-Octomod is an interesting new USB device which allows the generation of computer-controlled analog synthesizer control voltages, in the range of approximately +/- 5V.
Using a small open-source and cross-platform host application, you can control the 8 output channels of the Octomod through a simple OSC interface. The OSC interface lets you control the Octomod from a variety of software.
For example, Octofaders, above, is a Pure Data patch that lets you use an iPhone or iPad to wirelessly control modular synth gear.
The Octomod is available as a kit for $159 and assembled for $249.