To avoid any security issues we added a Samsung Galaxy tablet, on the Verizon cellular network, to our cellphone account. We use the "free" wifi, when it works,
for surfing but for any email or financial transactions the wifi is turned off and we use cellular access to the network.
You can also create your own wifi hotspot with most smart cell phones. You then connect via your own wifi network. Then you are accessing the cellular network through your cell phone.
In both cases you will be paying for the data charges on your cell plan. We went with the tablet for the simplicity and the convenience. Plus Verizon was virtually giving away the tablets when we purchased ours...
There are a lot of other fancy solutions, these are just the two easiest ones I'm familiar with...
EDIT: Go to the Modifications and Updates subforum, Here
, and do a Search on "wifi" there are several threads on other options.