A mashup of Twilio and Amazon, running on Google App Engine.
Look up Amazon.com book prices with any touch-tone phone.
Call (877) 265-8137. Enter the book's 10-digit ISBN number after the prompt.
The voice will tell you Amazon.com's lowest new and used prices for the book.
Go on, try it now!
Later, retrieve your lookup history.
To see the books you've already price-checked, enter your phone number here (just the numbers).