|Hardware wishes warning! This article or section documents a Hardware Wish List item, the features described here may or may not be implemented in future devices.|
FM/Digital Radio(DAB) Receiver
A nice feature would be a radio receiver: FM or even better: Digital Audio Broadcast (Digital Radio)
AM/Digital Radio(DRM) Receiver
This is something that gets left out of every consumer electronic device on the face of the planet. Why not include it for those interested in public broadcast frequencies, talk radio and news networks?
How about digital radio over AM: Digital Radio Mondial. There's an open source implementation thanks to Dream DRM Receiver. Don't know if the FPU-less ARM processor would be beefy enough for the signal processing.
Multi-standard Radio Receiver
Or even better a multi-standard receiver. There are combined receiver modules available for DAB/DRM/FM+RDS/AM+AMSS, eg. RadioScape RS500.
Why not going SDR? The AD9874 from Analog Devices is a general purpose IF subsystem that digitizes a low level 10-300MHz input signal with a bandwidth of up to 270 kHz. Interfaces are SPI for control, and the SSI could be connected to UART+external clock. SDR frameworks already exist from the amateur radio projects, such as DttSP and GNU Radio.
Family Radio System(FRS) Radio Transceiver
This is just another standard, for two-way communication. It operates on one of the unlicensed spectrum in North America (UHF). It's used for 1 to 5 mile walki-talky "party-line" communication in places like amusement parks, camping the wilderness, chatting between cars traveling in a convoy, ect. It's device to device.
Universal Software Radio Peripheral (SDR\USRP) Transceiver
The best would be generalizing the radio subsystem hardware for multiple transceivers and one or more antenna's. I have no idea how difficult it is to partition signal among antenna. However a general purpose radio subsystem would allow international shortwave, NOAA weather, AM, FM, FRS, possibly DAB/DRM/FM+RDS/AM+AMSS, etc., and maybe more. The USRP would only turn on for whatever specific task it was up to and then can shut off. Is this infeasible power wise?
Linux already has I think kernel level support for some general purpose radio interfaces.
Some sort of radio transmitter would be useful where you have a radio with powered and/or high quality speakers and would like to get better/louder sound out of a source on the phone. For example, in a car. This would also be nice for a alternative speaker-phone, but feedback should be considered.