While VoIP (Voice over internet Protocol) was once limited to stationary internet connections, today's technology has allowed VoIP to be as mobile as the cell phone service you currently use. To make VoIP work for you, you will need a data plan and constant use of the internet. At this time, the call quality may not be as good or widespread as your current cell phone. On the plus side, while at home or at work, with a wireless network, your calls would be virtually free.