Answer The Public (free and paid options)
Provides reports of the top questions and queries people are searching for in Google.
fraidycat (free)
Continuously creates a summary of the recent activity on the accounts you follow; results available by browser extension and standalone apps for your laptop/desktop (no mobile support).
Mailbrew (free)
Creates a summary of all the topics you’re interested across multiple platforms; results available by daily email.
Nuzzle (free)
creates a summary of all the topics you’re interested in on Twitter by aggregating the most shared stories by accounts you follow; results available by daily email.
Query Feed (free and paid)
Continuously searches Twitter for your search string; results available by RSS.
Refind (free)
Daily email with 10 most popular links relevant to your interests.
Signum (paid)
Emails you twice monthly with an analysis of over 300,000 blogs, forums, portals and social media accounts to keep track of the emergence of new trends at the earliest stages.