I've been using electronic tuners for more than 50 years. My first tuner was one of the old Conn brown box strobotuners. It worked fairly well, but it wasn't as stable as I would have liked. I used it to tune pianos, accordions, guitars, banjos, mandolins, etc. -- just about anything that was in the group I worked with was tuned with that tuner. Later, my father used one of the Peterson blue box tuners on his harpsichord. When I donated the instrument to a museum, the tuner went with it. So I started using iPhone apps. They were okay, but I wanted something a bit better. Then I saw the StroboPLUS HD on a Google search, and after reading about it, I decided to give it a try. It's much better than the old tuners. Much better than the iPhone apps. It's versatile. If you want to tune a diatonic autoharp to the Silbermann temperament, you can set that up as a preset on your StroboPLUS HD -- it takes about 15 minutes -- and there you go! It comes with a whole bunch of presets and "sweeteners," which you will undoubtedly find useful.
Yes, it cost more than the cheap ones, but it's a much better tuner.
Worth every penny!