BillGuard protects consumers against a kind of fraud-like activity it calls "grey charges." That's where companies sneak regular charges on your credit card, such as a free trial converted into a monthly subscription.
Once you sign up for BillGuard, you do nothing more. It monitors the world for fishy transactions and gets the refund for you, for up to three cards for free. It charges $80/year to protect up to 10 cards.
After it launched an iPhone app last summer, BillGuard landed 500,000 registered users. It did particularly well after the news broke about hackers attacking Target. The company has identified more than $1 million in fraudulent transactions, and $60 million in suspect, gray charges, it says.
It just launched an Android app in May, too.
BillGuard has raised $13 million so far from big-named VCs including Bessemer, Khosla, Founders Fund (Peter Thiel's and Sean Parker's fund) and Innovation Endeavors (Google chairman Eric Schmidt).