Leo van der Veen has released c74, an iPhone / iPod Touch app that let’s you connect your device with Cycling ’74’s Max/MSP 5.
Custom interfaces are built straight from within Max, presets can be stored etc. The external features some nice attributes for receiving accelerometer, GPS, compass, shake gesture and proximity data.
Communication between the apps does not rely on OpenSoundControl but in stead uses a straight forward communication socket, which offers a reliable connection.
c74 is available to purchase from the iTunes App Store, priced at $3.99 USD.