The homebrew KeepAlive app has been in Marketplace for about a month, and Jaxbot has just released an update to make it more reliable.
The backend has been optimized to keep connections longer, and the app itself is now stripped down to exactly what works and nothing that doesn’t, meaning your phone no longer cancels playing music, etc. Also, you can disable Keep Alive from within the app, with no need to uninstall it to disable its function.
The app remains free, though Jaxbox notes that donations would not go amiss, as bandwidth is turning out to be expensive.
Find the app in Marketplace here.