Dave Winer recently posted asking developers working on apps supporting inbound/outbound RSS to send him a post on it, so here is my post. I created an web app in 2023 using rssCloud and supporting inbound and outbound RSS called myStatusTool. I have working instances of a Node implementation developed by me and a PHP implementation developed by Colin Walker.
From this thread on Micro.blog, it looks like someone is preparing an iPhone app with many of the same features (BlogWarp). Cool!