I currently have my Hermes Lite 2 SDR connected to my Raspberry Pi 3 which is then transcoding data via an rtl_tcp "work-alike" protocol to send data over WiFi to my iPad (and Mac) for SDR.
Screenshot here:
https://www.rtl-sdr.com/forum/viewtopic.php?f=4&t=4896#p13511Other developers seem to be working on similar apps for Android to allow it to be used as the SDR display front panel for rtl_tcp from a Raspberry Pi.
Email me if you have a Raspberry Pi (or Mac) and a recent iPhone or iPad, and want to help beta test.
My iOS apps work with an RTL-SDR, Airspy HF+, HF+ Discovery, SDRPlay RSP1 & 2, or LimeSDR Mini plugged into a Raspberry Pi. Receive-only currently, but I'm working on low latency CW transmit for the Hermes Lite 2 by connecting a straight key directly to a Raspberry Pi GPIO pin.
http://www.nicholson.com/rhn/