Thank you and I suppose a prepaid data only chip is much cheaper than a prepaid phone + data chip. Right?
That's up to you to decide.
See the screen shots. The first is T-mobiles data passes. The second is AT&Ts.
You can get a $30 PHONE plan on T-Mobile now which includes 100 minutes, unlimited texts and 5GB data. The bad thing is that with anything but the T-Mobile iPhone 5, your data connection will be spotty for now. I'm lucky to get "4G" at my house where I get about 9Mbps now on my 4S. I drive a mile from here and I get edge speeds. Most of my area is edge.
On AT&T using the data sim, I get excellent "4G" speeds 95% of the places I go but have practically no data speed at all when at home.
So, I have a 3GB data sim card through AT&T that I use in my 4S.
I have a 3.5GB data sim card through T-Mobile that I use in my Nexus 7 tablet.
I have two T-Mobile $30 100 minute plans, one I use on a 3GS, one I use on my Nexus 4 phone.
Right now, I'm just having some fun even though I don't need that many phone/data plans open. I'm just having fun because I am paying less for all of these then what two iPhone plans cost me on AT&T. I'll likely drop down to the two data sim plans and one of the $30 T-Mobile plans.
I am using the 4S as an iPod Touch with data so I can use iTunes Match while I am out as well as the other phones capabilities including Tapatalk for calls.