On this weeks episode of Hak5, a popular electronics and hacking YouTube show, the presenters talk about reverse engineering and performing replay attacks on wireless devices such as a doorbell. They also talk about using the recently released Yardstick One which is a PC controlled wireless transceiver that understands multiple modulation techniques (ASK, OOK, GFSK, 2-FSK, 4-FSK, MSK) and works on multiple bands (300-348 MHz, 391-464 MHz, and 782-928 MHz), but is not a software defined radio.
Finally they discuss how to use the RTL-SDR and GQRX to stream received audio over a UDP network connection using netcat in Linux.
If you are interested in the Yardstick one, Hak5 also uploaded another episode earlier in the month showing how to hack wireless remotes by using the RTL-SDR to do the initial reverse engineering, and then using the Yarstick One to do the transmitting.
Source: RTL SDR