The two main LFOs can be controlled using the elements in the top half of the screen. The big knob in he middle sets the rate of both the LFOs. Additionally you can change the waveforms of the LFOs, detune LFO 2 and change its phase.
A third LFO can be used to modulate the frequency of the two main LFOs. You can change its waveform, rate and amount. The optional Brute Mode destroys the pretty LFO signal by adding cross modulation and distortion. It produces a harsh and unpredictable sound.
The iPhone can produce voltages in the range of about +/- 1V. You have to amplify the signal if you need +/- 5V.
The slowest possible rate of the LFO is at about 0.5Hz, the fastest rate is 150Hz.