I have a script that allows you to add proxies and when people enter a URL into the URL bar it will randomly pick a proxy and proxify the URL. The URL bar and button can be made to look just like any other proxy, you can put adsense ads and all that junk and you wont need to pay for hosting. It doesnt show the list of proxies you have so no one will know until they proxify a URL. How much would you pay for the script?
Take a minute to check http://forums.digitalpoint.com/showthread.php?t=46917 for free options we already have around.
I know of the free options there are, thanks for trying though. Read the post I made, this is not a PHProxy type script.