I doubt tunable hardware will ever be integrated into phones, given certification regulations,but there are apps for tuning RTL-SDR over USB OTG from Android.

I doubt tunable hardware will ever be integrated into phones, given certification regulations,but there are apps for tuning RTL-SDR over USB OTG from Android. I don't really know why an RPi was used in this example as opposed to a cheap used laptop that already has screen, battery and decent USB.