Local search and reviews service Yelp is the latest technology firm to file for an IPO, with a prospectus that reveals a lot of detail on its financials, including the popularity of its mobile apps.

Yelp now has more than 22 reviews of local businesses, with around 61 million unique monthly visitors to its website in the third quarter of this year, and five million unique mobile devices using the company’s apps.

In the first nine months of 2011, Yelp generated $58.4 million in net revenues, up 80% year-on-year. It’s not profitable yet though: its net loss for that nine months was $7.6 million.

Yelp thinks mobile will be a key factor in its future growth, too. “Mobile devices provide an ideal platform for people to search for local businesses due to their ability to identify consumer location and provide all the benefits of digital content to consumers on the go,” explains the prospectus.

“Our mobile app is an ideal way for people to discover great local businesses. It combines our reviews and other relevant information with knowledge of the consumer’s location in an integrated experience. Our mobile app also provides new ways to contribute content to our platform through features that let consumers ‘check-in’ at local businesses and submit photos and ‘quick tips’ directly from their smartphones.”

The filing also talks about plans to expand Yelp onto “automobile navigation systems, web-enabled televisions and voice-enabled mobile devices”.