If you have some spare rpis and a radio it can be pretty interesting to set it up to check on it, tho there are no "real world" utilities, since as the other comments mentions, it is illegal to use that as it is

Well, you can open the url in your browser, and inspect the code that is also on the github repo ;)

Technically, the pis gpio headers can act as a really, really short antenna, so it kinda works without, but you're right

After seeing some comments, I'd wan't to specify something that isn't really mentionned in the readme or anywhere but, this project doesn't aim to replace professional setups nor cover long ranges (that would be absolutely irresponsible to try to). I think it's mostly aimed to cover a house, garage or to be in a sort of "big faraday cage" for your own personal use, if you have some pis and radios laying around.

There is no "may be subject to local regulations and laws" (quoting from the project page); operating such a rig is flatly illegal in any civilized country. RF regulations are enforced by authorities at the national level and you can bet that if they have to go to the trouble of tracing down the RF signal from this (very easy to do), they will be bringing the legal equivalent of a can of whoopass with them. And they will not be mollified by claims of personal use.

Again, the project you forked from literally tells users never to attach an antenna; they have enough RF knowledge to know a tiny bit of signal can go a very very long way. You clearly do not.