It won't solve the business card issue, but you could see if your cell provider offers a "femtocell" device. They're sort of like a wifi hot spot, but create a personal cellular zone in your home and route your calls via the internet. It's seamless - you receive and place calls and text messages as you normally would.
I have an AT&T Microcell, which Cisco makes. It is initially configured to only recognize your phone, but you can add other numbers using their website. I've heard that if your contract is up and you threaten to cancel due to lack of a signal, they may give you one of these. I had to buy mine but it was worth it to finally be able to use my cellphone at home.