Dunno how much I'd trust downloading an app from a site, let alone buying a test kit from one.
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Is it a blood test, if so that might be more dangerous.
It's not an 'app' it's a blockchain with a bitmessage forked data storage protocol where the big data such as pictures and messages can be stored off-chain. I'd go as far as to argue that the Particl decentralised market is the first working dapp.
For the test itself I'd guess it's an antibody test, as the virus would require RNA replication, which currently needs to be done in a lab. Most antibody test typically require a few drops of blood and can be done at home.