I'd do the visa check card. Bank of America is very good at protecting their clients from fraudulant charges. Sometimes they will put a hold on it and call you to make sure that you actually made the transaction. Not to mention they have free online banking where you can pay your bills online through the acount and view your account frequently to be sure nothing fraudulant is going on.
Also, most of the time when online purchases are made, they ask for the 3 or 4 digit security code on the back of your card as verification that it is you making the purchase. If you card is lost or stolen, more than likely they are not going to be using it to make an online purchase because if they put in a shipping address that will lead them straight to you.
Also w/ Bank of America, they IMMEDIATELY refund your money when you report fraud rather than most banks where they investigate it first and then give you the money back if it can be proven.
I think a visa check card is probably the best way to go. In order to prevent yourself from spending more than you want to be able to, open a checking and savings, deposit all your money in the savings and move it over the checking (which the visa check card will access) and use what you want.