A few days ago Google announced this crazy new feature that allows you to attach actual money to Gmail messages. We've discovered the feature is actually up and running, you just have to be invited!
To get invited, someone just has to send you some amount of money over Gmail - a penny will do fine. So, find someone who has access to it, give them your email, receive a penny, and you're in!
If you happen to find someone who has access, and they send you a penny, you'll get an email like this. Clicking on "claim money" will take you to the special wallet site that gives you access.