Basically this is an ARM-based embedded Linux system. So regarding the hardware you are pretty much covered. What is at least as important is what kind of software and connections options are delivered with it. Unfortunately the data sheets do not specify what software this multi-function card reader comes with.
GPRS is a data connection protocol which supports the internet protocol (and thus TCP/IP and possibly HTTP(S)). So for the data transport you can use any normal internet connection. You should however make sure that your applications can handle intermittent transmission errors or lost transmissions. This is something your application should gracefully handle anyway, but the chances of encountering problems is obviously higher.
I don't see why you need a sandbox, but you should contact ACR to make sure you can develop your particular application. You may need a development toolkit.