I don't think you need to pay for anything either. I've seen ads from companies claiming they go above and beyond what you can get from sites like Credit Karma; I admit I don't know exactly what they claim to do, but I'm suspicious.
If you regularly monitor your accounts you will catch fraud on legitimate accounts. If you have CK and regularly order credit reports* you will catch accounts that are fraudulently created in your name. I like to rotate by bureau and get one credit report every four months. It's not the "daily monitoring" these companies say they do, but IMO it is sufficient to catch fraud.
*The only place you should order credit reports from is http://www.annualcreditreport.com
(either online or over the phone number they provide) - there is no need to pay for one.