I had a problem where I want to be updated on new submissions to arXiv about quantum computing. Unfortunately, it seems that arXiv only provides RSS feeds for different categories, whereas I would like to get the feeds matching a keyword search.
To solve this problem, I wrote a small proxy feedproxy to fetch RSS/Atom feeds and filter out items that don't match a certain keyword.
I start the proxy by running the program along and specify the port it should listen to
feedproxy [PORT]
Then to fetch from arXiv's computer science feed I point my RSS feed reader to
http://127.0.0.1:[PORT]/rss.arxiv.org/rss/cs?keyword=quantum
where [PORT] is the port feedproxy is listening to. The query parameter keyword=quantum tells the proxy to drop any items that don't contain the keyword quantum (case insensitive).