DesignByPaul released FM 304. This massive FM synth app includes 3 different FM engines. Each of those offers 4 operators with their own sequencers and effects. The iTunes description does not indicate if this supports AUv3 or Inter-App Audio or anything... I've sent Paul an email for clarification.
FM 304 iTunes Description:FM 304 is a set of Three 4 operator FM synths, each with integrated sequencers and onboard effects. FM 304 exposes all synth parameters with a one knob per function paradigm, allowing for quick, fun and intuitive real-time manipulation and creation of tunes and sounds.
— 3x four op FM synth
— 3x LFO
— 3x 16 step sequencer
— Effects: delay, reverb, chorus
— 100 save slots
— 8 algorithms
— Note frequency quantize