Finger Pro has both of its iOS apps, MoDrum & BassLine on sale for US $1.99:
The two apps are notable for their implementation of MIDI sync over WiFi, demonstrated above.
Here's what they have to say about the latest versions:
With the latest update for MoDrum (v1.1) and BassLine (v3.2), Finger is the first to fully exhaust the opportunities provided by Apple’s CoreMIDI API. Tempo-sync apps on your multitasking-capable device, or get the ultimate band experience by syncing several iOS devices with each other or your favorite DAW!
We sat down with Rob to discuss the creative process and what lead him to using a modular