The Hak5 Key Croc is a pentesting tool designed for emulating USB devices such as keyboards. It is commonly used by pentesters for keylogging and keystroke injection. It has some advanced features like keyword detection which can be used to detect when a certain word is typed. Under the hood it runs Linux on a quad-core ARM processor.

Over on the Hak5 YouTube channel Glytch shows us that he's been using the Key Croc as a remote RTL-SDR server. The server is setup through a payload script, which is then activated by typing "setup" into notepad on a PC. The keystroke logging and keyword detection feature detects the setup keyword, and runs the payload script which installs the RTL-SDR drivers and rtl_tcp server all while using the keystroke injection feature to output the install progress. Then it is a simple matter of plugging in an RTL-SDR, and connecting to the rtl_tcp server on a program like SDR#. 

Glytch notes that this is useful because you can run the entire Key Croc server and RTL-SDR on a portable battery pack, and now you have a remote SDR that you can place anywhere within your WiFi network.