r4t Smart   Rummble lets you check in and review locations with a tweetThe location-based apps market is a crowded one. Aiming to get the upper hand on its rivals, Rummble has just launched a pretty awesome new feature.

The service, which melds Foursquare-style location sharing with Yelp-esque social reviews, has now launched the ability to check in to a location and review it via Twitter.

Simply sending a tweet containing the hashtag #Rummble, the service’s back-end tech will do the rest. As the London-based start-up’s blog notes, sending the following tweet: “Hanging out in Joes Cafe, norfolk street Cambridge. Great coffee and free wifi. 7/10 #rummble” will result in Rummble working out that you’re in Joe’s Cafe, where is , what you think of it and give it a score out of ten.

Impressive tech for sure, and it takes the pain out of checking in to a location. Sending a quick tweet is likely to be easier than loading the app, waiting for it to find your location, checking in and writing a review. Rummble admits the technology isn’t perfect, noting that “Computers reading natural language is always tricky; computers reading 140 characters is even trickier. The more info you include, the better the chance Rummble will guess where you’re talking about!”

It’s well worth trying if you’re a Rummble user. However we think the way for Rummble to really get ahead here is to support checking into Foursquare and Gowalla via that same tweet. Rummble already reads check-in tweets from rival services. To send them the other way could be a killer app.

Rummble has some impressive technology running behind it. The way it recommends locations to you is based on complex academic social theory that in a fair world might give it the upper hand over its rivals. However, in the face of the marketing might of its big US competitors it’s still struggling to be mentioned in the same breath as them.

If the Rummble team can continue to push ahead with impressive technological leaps like this they may yet make the leap to the mainstream.