First, the app only dumps saves from the original cart but can´t upload it to one in general.
Second, even the dump doesn´t work on my SS. I tried it, the app dumps something, but the .sav file can´t be opened with pokesav which I could only try it with because I don´t have SS as a rom. But anyway if PokeSav (.03a for HGSS) can´t open it, I doubt it would work with an actual rom.