The Strange Agency has released the Donut app for iPad which they say can record loops in two dimensions. Here's their description of it...
You can use it like a phrase looper, by recording horizontally while using the step controls to step through vertical recording position. You can use it as a realtime processor by using ThruRecord mode. You can record and playback at completely differently speeds. You can even record backwards! You can record and playback diagonally across the Donut surface, creating glitchy staccato sounds. You can record and playback with multiple heads, recording or playing multiple positions at once. You can spread the heads vertically to access different portions of the Donut, or you can spread them horizontally to create an echo effect.Pricing and Availability: