We’re one week away from what is usually a very difficult night to score a reservation at a nice restaurant, so if you haven’t acted yet, you may want to check out a brand new SF-based service called Rezhound.

It’s built on top of OpenTable, in the sense that Zynga was originally built on top of Facebook.

The way to use it is when OpenTable tells you there is no availability at your restaurant of choice, go to Rezhound and make the identical reservation request–including the size of your table, date, and time.

Rezhound will then automatically ping OpenTable every few minutes with your request until a table finally opens up.

This happens more frequently than you might imagine, as people’s plans change and they have to rearrange their dinner reservations.

So, by acting as your reservation assistant, Rezhound can help you get in to restaurants that otherwise may seem impossible to crack, like Flour + Water, Cotogna, and The French Laundry.

Rezhound is the brainstorm of Reed Kavner, whose day job is as a product manager at StarMaker, the mobile karaoke app company.

Kavner says he became frustrated when he and his girlfriend could never get into Nopa near the Panhandle, so he set out to solve that type of problem.

The way he built Rezhound, starting last October (it launched on January 14th), should serve as an inspiration to anyone who thinks launching a new service would be way too difficult and technologically challenging.

To teach himself coding skills he read Learn Python the Hard Way by Zed A. Shaw.

Working nights and weekends, he utilized the Google App Engine to build the back-end. On the front end, he took advantage of Twitter’s Bootstrap framework.

“The resources are out there to do something like this,” says Kavner. “The languages to write code in are far more like English, with words easy to understand. It’s a lot less intimidating than in the past.”

Whenever he came upon a problem he didn’t know how to solve, Kavner turned to Google, entering “How can I…?” as a search query.

“People just rushed to answer every question,” he says. “They want to be helpful.”

Because the underlying technologies are essentially free, Kavner says the site only costs him a few cents to a few dollars per day to run.

He isn’t making any money off the service, which he calls a “side project, just a fun thing to do.”

Written in HTML5, Rezhound works fine on mobile devices, though it is not optimized for them yet.

So far, just weeks since its launch, Rezhound is able to find reservations about a third of the time for its users.

“That’s double what I was expecting,” says Kavner.

Given OpenTable’s reach, Rezhound works far beyond San Francisco, at some 26,000 restaurants in 19 countries around the globe.

Kavner says the early “hot spots” for use are in San Francisco, LA, New York, and Chicago.