Pickups are a nice addition to a ukulele, even if you only us them to practice with an amplifier. I have long been an advocate of MiSi Pickups and have installed dozens. Two more today. Containing a pre-amp, a simple one minute charge connected to 110 and you can play through an amplifier for 16 hours. No battery to change, simple to use and very high quality, plus you get a nice strap button to boot.
This is all that you see on the outside, the strap button. The piezo cable is hidden beneath the saddle.