They are a very simply ASK (OOK) transmitter/receiver. Even sending digital data, like you would on a serial COM port does not work.
I have to disagree... They can be used to make a wireless no-handshake-232 (within the bps range it can handle), although a protocol with packetized checksum'd data and retransmission of bad packets gives a more secure transmission, but hey, this is temperature data and the receiver could accept only a certain deviation between two sets before discarding the last data sent.
Many wireless doorbells/oven thermometers/weather stations etc. use similar ASK modules and transmit simple digital data with no checksum or anything and they rarely fail, as long as they're in range and there's nothing jamming them.(Makes me think... My SO likes her meat a little more rare than I do, so perhaps I should make a jammer/"translator" to get an oven roast more to my liking )
For more secure transmissions, FSK is much better.
As for your current code, hard wire the two processor's data lines [...]
I might be wrong, but I got the idea that only the receiver side contains a controller.