My Costco Kirtland Signature in-the-ear models use a Bluetooth connection to an iPhone app.

The app does the adjusting between 4 presets that can be adjusted by the aid tech pretty much anyway you want.

You can also create "favorites" as the app allows separate volume control for each ear. Thus you can set the aids to any desired volume(s) and save and recall, where as the presets created by the technician does frequency and tone changes.

Then you get phone call ported to the aids, with the microphone on the iPhone providing talkback. This is possibly the best feature.

I would expect that a lot of other manufacturers to go the smartphone route in the coming months and years as Coscto is killing the market with this technology currently.