Apple (NASDAQ:AAPL) and Google (NASDAQ:GOOG) are each taking steps to improve application discoverability in their respective app stores, including a new search function from Apple that tries to make a more educated guess at what smartphone owners might be looking for. However, there are still plenty of third party app discovery services and app search firms that hope to make finding apps even easier. One is Appreciate, which has been likened to doing for apps what Pandora does for music, and is based on a real-time bidder system tailored specifically for app recommendations. The bidder is built on top of the Appreciate recommendation engine and is designed to allow mobile app advertisers to most efficiently get quality users in large volumes. There are also a number of firms that continue to focus across platforms, such as Quixey (though its recently launched consumer app focuses only on Android) and Appolicious, a firm that offers white-labelled app discovery services as well as its own vertical-based directory. For more on the quest for the ultimate mobile app discovery service, check out this FierceDeveloper special report.