SSB receiver? There are a good few simple SDR designs out there too if you want something more modern.
Maybe a beacon of some sort, low powered morse temperature transmitter or foxhunt target.>>764
Not particularly - radio amateurs have an allocation in the 2.4GHz ISM band, but all countries prohibit the use of any encryption by amateurs (WW2 espionage fears + it would prevent the regulators from ensuring that the bands are being used for non-commercial use only). You can do so, but it has to be open and you could never use anything like HTTPS over it.