No, it is a router. It only connects to your Modem (DSL/Cable).
The router itself apparently will have two SIM slots, one for you home #, one for your mobile.
The Home SIM card will basically be your current home #, ported over to T-Mobile so you can take advantage of the WiFi calls.
I don't really understand about the mobile part, since the cellphone you used would simply connect via UMA, why would you need to put your SIM in there. What I think they meant was, if you have two home #'s, you can port both and the router will support both #'s.