"Aircard" is a trademark name for a range of modem
devices that connect through cell networks to deliver data to your computer. These devices can be cards that insert into a card slot on your computer, ones that connect through your USB port and ones that stand alone and connect wirelessly to your computer (mifi). There are all sorts of them sold by many vendors.
You can also tether some cell phones to your computer. This allows you to have both a phone
and a data modem
The most important thing for all of them is to get an unlocked GSM/quad band version. In the US, they will be locked and for certain carriers, they will be CDMA devices and not usable outside those systems.
Yes, these devices must be used with a data plan of some sorts. In the US, you have to sign up for an expensive monthly plan that usually requires a two year commitment from a single
vendor that cannot be broke without paying fees
. In almost all other more enlightened telecom systems around the world, you simply go to the local telecom of your choice and ask for a sim card. Actually, you can pick up sim cards in almost any store of any type and even through street corner vendors. Heck, the marina restaurant here sells them. They usually cost $1-30, but come with that value already on them - so in essence they are free. You then put money
on them and use them to feed data to your computer at whatever $/GB they charge. Here in Panama
, it is $15/GB. When they start to run out of money, you send more money to them by either phoning a number, using a website, or taking them to a vendor (which is just about everyone here).
I don't know which wifi system you are asking about. There are many, many types and the choices are vast of which models, how they operate and how they connect to your computer. Google
around for bitstorm, islandtimepc and wirie for commercial
systems for a start (there are so many more but I can't remember them all). Also do a search on this board for wifi - it has been discussed in excruciating depth
and detail for several years here.
I don't mean to be vague or unhelpful, but without knowing where you plan to use it, how you want to use it, what your budget
is, etc, it is difficult to be more precise.
If you will only be in the US, you will be stuck with whatever carrier you choose for cell data.