RigPi can be used on any mobile device that provides an Internet browser. Since RigPi uses a browser, no app is required (other than Mumble for audio). Here are several samples of how the Tuner window appears on mobile devices.
iPad Pro
Single connection to one radio, landscape mode
iPhone
One connection to RigPi, one radio, Tuner, portrait mode
One connection to RigPi, one radio, Tuner, landscape mode