It's a site that simply catalogues every IP address seen on the DHT. If you're torrenting, and you're leaking that data publicly, this site simply compares it.

https://www.godaddy.com/whois/results.aspx?domain=iknowwhatyoudownload.com

The site is registered through godaddy, and claims of it being a Russian site is simply meant as a scare tactic. Any website you connect to without a VPN immediately knows your IP address anyways - it's not some sacred thing you have to protect against people knowing.

Hell, if you're concerned with it - plug your VPNs IP into it; you'll see the torrents that others on the VPN are seeding from the IP address you're using.

If you're using it on mobile, it's not likely that anyone is torrenting on mobile, so unless someone is really doing dumb shit - it's not likely it'll list anything. It's a useful tool to have under your belt to see if your bittorrent client is leaking data.