Hi,
(shell-command) doesn't work properly in Android apparently because it checks for the presence of environment variable HOME and it isn't always defined in this OS. As it doesn't find this variable it chooses CMD.EXE for executing as if it were Windows, which obviously doesn't work. However PATH seems to be in all devices I've checked out. AFAIK it also happens to be present in OsX and all Linux flavours, is that right?
Best regards