Yelp is making a huge splash on Gowalla and Foursquare by adding Check-In features for the iPhone this past week. It has plans to be on the Droid and other mobile operating systems very soon. 26 Million people connected with local businesses with Yelp last year and has over 1.25 million users in their community. The new release of the Yelp Check-In system is shaking up the competition. Mashable did a poll on who would win in a fight of location based mobile services which included Yelp, Gowalla and Foursquare. Of the 2495 votes Yelp received only 26% of the votes. That was at the brink of Yelp adding the Check-In feature and iPhone users are still updating to the new Yelp 4.0 software. I would like to see a similar poll at SXSWi this coming March, as we could see significantly different results.  Much like Foursquare and Gowalla, the sharing feature of the new Yelp app allows you to tell your friends on Twitter / Facebook.  Also enabling the push feature allows you to get instant alerts of where your friends. Yelp allows you to turn on “weekend only” push alerts which is new to the mix.

Why Yelp has Gowalla and Foursquare freaking out?

Yelp Monocle – this is the Augmented Reality feature Yelp added last year and has made significant updates with the new release including a new “map” feature that will move with you. Having the reviews, distance to location, type of business, and price point show up is a nice bonus with the Monocle.

Reviews – Foursquare and Gowalla both have Tips/Review systems but have a lot of ground to catch with the over 9 Million business reviews which puts Yelp in a sweet spot. Not only will you be able to see who posted the review but how many times they have been to that business.

Filtered Reviews – In 2005 Yelp added in a Review Filter which has evolved and helped businesses with credibility. The algorithm of how this is filtered is going to be quite a challenge for the competition.

Photos– The ability to add pics is a must.  When checking in on Yelp you can add pictures of the amazing dinner you are having or the coolness factor of the atmosphere. Foursquare and Gowalla do not have this as a feature.  You can however use third party applications such as Tweetphoto to check in on Foursquare just by simply taking a pic.

Maps- A Map that will show you the Check-Ins of your friends nearby and Check-In count next to your Yelp Star Rating once you write your first review.

Gowalla and Foursquare are focusing forward with virtual goods and a gaming aspect that Yelp has yet to release. It should be an interesting road forward.  Based on how Twitter spiked and took off in March ’09 ,whichever location based service company shows up to SXSWi in March with the most offline collateral and banners for all bars, restaurants, keynotes, panels etc will probably be the clear winner for 2010. Let’s see if Mashable’s poll will shift then… What App do you use to Check-In and what do you think of the new Yelp app?