I’m a big fan of Yelp.com because of the richness of information plus the fact that they do a pretty good job of keeping it real and not getting bogged down with shills. Yelp also has a great mobile site that allows you to search through their listings and find something directly from your mobile phone. This service is particularly useful when you’re out and about in an unfamiliar area and need to find a good place nearby.

So I made this mashup. You can play with it here. Here’s a pic.

The idea is that you can drag around the Google Map, and then when you click on a location, it will generate a QR code for Yelp’s website which allows you to see what kind of restaurants and nightlife are around that exact point on the map. Pretty cool, right?

In order to make this happen, there’s a lot of web services going on in the background. First, there’s the Google Map. Pretty basic and well documented. Once you click an overlay though, Google only gives you latitude and longitude of the point, but not an address. So I found this great Google Reverse Geocoder online and am using that to convert the lat/lon into a street address.

From there, you can build the URL for mobile.yelp.com, but it ends up being a VERY long URL and consequently, the bar code gets to be gigantic. So once I have the long URL then I’m sending it off to tinyurl.com to shrink it down. Finally, you take the tinyurl and generate the bar code using Kaywa.com.

Four web services, all done with a few lines of Javascript. If you look at the demo, then all of the source code can be seen there.