Referral Marketing Software

[koryb1]

Has anyone used any Referral Marketing software? I'm looking for a tool that would:

1. Invite our customers to refer us to their friends.
2. When they send a referral email, they'd be rewarded with a coupon for doing so.
3. The email their friend receives also includes a coupon.

Software and web-based apps exist that do this, but when I search for it there are tons of results. Many want a steep percentage of the captured sales which seems crazy (I'm happy to pay a reasonable monthly fee which seems more fair).

If you any of you have found such a tool that you like I'd sincerely appreciate the suggestions.

Thanks in advance!