The biggest problem in this space isn't a transaction system, the coding, or even the idea. I highly doubt that companies are willing to 'share' their virtual currency since they work closer to gift cards. It's getting big companies like Microsoft and Amazon and Zappos to convert from their virtual fun bucks back into real money. The barrier to entry to work with those guys are HUGE.
The closest thing you can have is an automated system that keeps enough gift certificates from different places to allow exchanges for a fee. (ie. exchange $50 Amazon gift card into $50 Zappos gift card for a buck or so.) Even then, some places like the Xbox 360 points don't have any way of giving to people once it's on your account.
This doesn't even count the fact that some systems, like WoW gold, makes it illegal via usage contract to convert virtual money into real cash.
Not to mention isn't a lot of the advantage of selling gift cards that they go unclaimed?
I'm not really sure what is the real advantage of a virtual currency system. I don't want to put any substantial amount of money in virtual currency. Also in order to buy something with a virtual currency there has to be a market for the currency, and the virtual currency is always going to be worth (substantially) less than regular cash. Maybe I'm missing something big here, but I don't see how this could ever be workable.
The closest thing you can have is an automated system that keeps enough gift certificates from different places to allow exchanges for a fee. (ie. exchange $50 Amazon gift card into $50 Zappos gift card for a buck or so.) Even then, some places like the Xbox 360 points don't have any way of giving to people once it's on your account.
This doesn't even count the fact that some systems, like WoW gold, makes it illegal via usage contract to convert virtual money into real cash.