The ClipMic Digital (CMD) by Sennheiser gives your iOS devices the capability to capture high fidelity audio on the move. CMD is powered by Apogee's analog to digital converter which allows the Sennheiser ME 2 lavalier microphone to put it's omnidirectional, condenser magic to work. This is a $199 complete system for audio capture, which means you do not have to purchase anything else outside of the CMD to get awesome audio.
It performs very well and really opens up the world of productivity if you're invested in the iOS ecosystem. The CMD works as if it was a native Apple I/O device; therefore, it works with nearly all AppStore apps. For example, it works really well with GarageBand. I also heard through the Twitter-vine that it works with Periscope:
Update: It is confirmed the ClipMic Digital works with Periscope. NOICE!
Ultimately, if you're on somewhat of a budget, own a iOS device, and are in need of a Lav microphone the Sennheiser ClipMic Digital powered by Apogee may be your solution. If budget is not of a concern and you have a means of recording audio separately from a transmitter/receiver the Sennheiser EW 112-P system is still the best system hands down. Check it out: