Mention iPhone App
You can search for 3 different kinds of relationships.
1.) User Mentions
2.) References (backlinks)
3.) Search Terms
User Mentions
User mention is when someone refers to someone else in their post using the 
Usage
To find all recent posts that mention someone, type their 
For example, when I narcissistically searched for myself I found plenty of responses to my own posts that I never knew existed, novel ways of using SteemData, ideas for SteemQ, and other goodies.
Backlinks
Like user mentions, backlinks are a powerful way of discovering replies, and broader discussions around ideas sparked by particular posts.
Usage
To search by backlinks, simply paste a link of the original post into the search.
For example, here you can see all posts that mention recent busy.org announcement.
Keywords and Phrases
While User Mentions and Backlinks are very precise tools, sometimes its useful to look for areas of discussion around a broader topic.
Usage
Treat the search box like a basic search engine. For example, here are the results related to machine learning.
To search for keywords and phrases effectively, follow these strategies.
Post Includes ANY of the keywords
machine learning
Post Includes ALL keywords (unordered)
machine+learning
Post includes a phrase (ordered keywords)
"machine learning"
Mix and match (machine learning posts that mention 'brain')
"machine learning" brain
Exclude a keyword (machine learning posts that don't talk about 'brain'):
"machine learning" -brain
Closing Thoughts
Mentions is a concept application, and as such, it has many rough edges.
I would love to hear your feedback...
is the app useful to you, and what are you using it for?
what kind of problems does it solve?
how can I improve it?
You can find the Mentions App Here