One Juicer works essentially like Google Alerts, allowing you to track new applications by keyword and receive e-mail notifications as soon as new apps matching your keywords hit the App Store. So, for example, enter in “social networking” or “poker” and you’ll be e-mailed whenever new apps containing those terms are listed. One Juicer also gives you a login so you can manage the keywords you track.
The service's developer sees One Juicer being used primarily as a competitive intelligence tool, writing, “As developers, we are faced with competing apps entering the App Store daily. You can imagine it gets quite tedious to search certain keywords related to your apps daily. And if you slack off it's even more frustrating when you find out days later that a new competitor has moved into your space.”