Combine Subreddits for Android
This app works by constructing a URL from your subreddits. You can do it yourself, for example https://reddit.com/r/Health+Fitness+Funny. The only thing that it will take too long to type, if you are following 10+ subreddits.
Q: Is it fast?
A: Yes, the data is loaded in one request (no individual subreddit scrapping)
Q: Does it harm Reddit?
A: No, we are making a single batch request. You can do it by yourself in the web browser
Q: How to filter posts?
A: Unsubsribe from subreddits that you don't like, custom filtering is not supported by design
Alternative way to combine subreddits is to create a “multireddit” by yourself: http://wikihow.com/Create-a-Multireddit-in-Reddit. This app works more like an RSS reader.
Currently the Combine Subreddits app displays only "hot" section, because it seems to provide the best balance between quality of the content and the frequency of updates (30-60 minutes). If you don't agree, or you want to have a selector, let me know in the Google Play review.
The code for this app is open, developers can submit their ideas as a pull request:
https://github.com/AlexSheiko/CombineSubreddits