I have installed the MiSi Simple Jack Uke pickups for years with great results. Now I am about to try their latest invention, a pickup with both the under-saddle piezo pickup and also a tiny new microphone, so small to be almost unseeable.
The Treo Air comes with a double wheel volume control, one wheel for the under saddle piezo pickup and the other for the tiny microphone. The control wheels are accessible from the sound hole.
Here is a close up. Can you find the microphone? The round blue edged things are not batteries but capacitors. They store electricity and slowly send it out to power the pickup.
Here is the answer. The microphone is seen inside the red circle. it is reputed to be powerful enough to pickup the remarks of your audience if turned all the way up. Maybe you would rather not broadcast that.
Heres a comparative photo of the new Treo Air and the veteran Simple Jack Uke. A difference in length, more wires to stuff into a ukulele, and a small difference in weight. My scale shows the Treo Air weighing 34.26 grams and the Simple Jack 28.20 grams. It will be some weeks before I will be installing the Treo Air but when I do I will report my opinion.