Most modern hardware PBX's will do this. Of course you will need a POTS in and a POTS for simultaneous outbound. However, this is a hardware solution. You're better off with one of the unified messaging providers in this case.
That Linky seems rather spendy. Wonder if the price will come down?
So I'd need two landlines? Hmm... You're sure the Linksys can do that?
