Yelp launched its iPhone application back in 2008, but announced expanded functionality for the user-review site's foray into smartphone app stores. Today the Yelp blog showed new location-game features for the app, now available

for Android, Blackberry and Palm Pre.

Spurred by the SXSW-fueled popularity of check-in games, Yelp recently released its own check-in feature. In an upcoming update to the app, users can also unlock Badges, and earn "Royal" status in return for repeat check-ins at local businesses.  While they know they aren't "the first ones to offer check-ins," they guess they "probably won't be the last..." But the added elements do make the app more fun and they say it compliments their existing mobile offerings, connects people and promotes local businesses.

Anyone familiar with Foursquare will recognize the use of Badges, the same term used for the prizes given for filling certain requirements such as visiting several karaoke bars or food trucks. Yelp users can earn a "Sushi Sensei" badge, for example. The same can be said for "Royal" status - instead of Foursquare's Mayors, a user can become the Duke of a shop, Baron of the neighborhood and King of the city.

The review site has been collecting data on the success from moving to mobile. The post lists related data showing that on average, more than one in four Yelp searches come from the iPhone app. This rate increases on the weekend when more users switch from Web-based searches to on-the-go queries. Showing success rate in a different format, given figures show the following:

over half a million calls were made in May directly from the Yelp iPhone app
nearly one million people generated directions from the app
Yelp for iPhone had over 1.4 million visitors in the last thirty days

ReadWriteWeb expects Yelp to leverage special check-in coupons, the only Foursquare function not adapted to the review site's app.