Here are some exemples of M2M communications. Just click on the miniatures for a larger size
You can notice that in all cases, there is a client, which will be an android in our case, communicating with a device you want to interact with through different ways : wired connection or a wireless one, using wifi, bluetooth, the cloud…
We can extrapolate this analysis to this following simple scheme :
C1 corresponds to a direct link between the machine and the android client, with a server linked to the android which can essentially contains additional information, using a database for instance.
The C2 case is a communication between the client and the device which passes through a server.
The last case consists in one or multiple devices connected to a server and communicating with the client, which is linked to the server aswell. Furthermore the client is in contact with another server which has the same role as seen in the Case 1.