Doc you dont need a sim to go on line use the wi fi of your phone link to broadband as you do with the kindle , then download app , its a good idea not to have a sim in the phone if your using it for FPV as a phone call can over ride the FPV mode on some apps
What Jackson has linked you too, is also a good route to go
a few things to be careful about is what ever you use it must not be able to blue screen or cut off is the FPV signal get weak
and what is the range of the wi fi most are only 300 mtrs max