FantaStick (App Store link) is a minimalistic remote interface for the iPhone for use with software such as Max/MSP or Pure Data.

Features:

• Minimalistic, fullscreen control area with nothing on it but what you provide.
• Multitouch-events on the device are forwarded to your host via UDP. Information includes the touch state (begin, move, end) and coordinates.
• Designed for no-hassle: zero-click startup, the device does not sleep or suspend network connection, flicker- and lag-free.
• Displaying images (fetched with URLs) and caching them locally for use on non-networked locations.
• Basic drawing with lines, boxes and text.

Visit http://pinktwins.com/fantastick for quick start and usage examples.

NOTE: this app works together with other software. When launched you get a black screen, what happens then is up to you. Visit the website for examples and documentation.