Interesting concept that you can incorporate into your website or blog.
If you really know your area of expertise or consider yourself a consultant, you can let people call you after they have paid for your time. The service is named Ether and they issue you a phone number that let's readers call you.
You set the rate to charge, put a button on your site and if someone wants your advice, they click and pay. If you are not available based on the schedule you input, Ether will tell the reader when you are next available. Ether cut is a mere 15% and they handle all of the billing.
Here is a link to one of their pages that does a pretty good job of explaining the actual process.
From their FAQ page:
What happens on a call?
You earn money based on the rate you've set. Once you've placed your Ether Phone Number where you want people to see it, your phone only rings when someone is ready to pay for what you say.
A customer will dial your Ether Phone Number and Ether will call you at the number you selected. You can choose on the fly whether or not to actually take the call. For example, Ether will tell you that you have a customer ready to pay your rate of $90 for an hour and willing to wait 3 hours for a call back from you. When you answer the phone, you'll hear:
* Press 1 to take the call now and earn your $90 for the hour you talk
* Press 2 if you can take the call within 3 hours, and earn the $90 when you're ready
* Press 3 if you cannot take the call now nor within the 3 hour time window
