You can do 1 of two things. you can purchase the tethering plan through your carrier, I think it's about $30/month.
Or, you can purchase a 3rd party tethering program such as tetherberry, but using it without a tethering plan is against your carriers TOS, so the bill will be astronomical if you get caught.
You will be able to do everything, at reduced speeds that you can do with wireless internet, but keep in mind that there will be a "cap" on usage, and going over will result in a big bill.
08-18-09 03:26 PM