Years ago, Philips made the TDA7000 then replaced it with the TDA7088 that works from a supply as low as 1.8V. You can use the simple voltage stepup circuit in a Joule thief or solar garden light to stepup the 1.2V. The IC is not available from Philips anymore but a Chinese company copies it and a radio with it is available at The Dollar Store costing only $1.00 with battery. I got two of them for free by buying cheap things in the store.
The radios are awful for sound but might be good enough for DTMF.