Recently, the remote for my Sony Blue-ray stopped working. I tried the typical recommended things suggested by Sony forums but gave up. I proceeded to find an app to use with the device. After several failed attemps installed useless ad filled apps. I came across this app (Video & TV SideView: Remote – https://itunes.apple.com/us/app/video-tv-sideview-quick-remote/id594171390?mt=8), which is actually recommend by Sony but it was burried in their support page https://www.sony.net/united/userexperience/support/en_ww/wont/030/02str-dtl.html. The app works on Android and iOS, although I just tested the iOS version, you can get the Android version from the link above. On iOS it currently has a 3 out of 5 rating but worked just fine for me on the Sony model BDP-S2100.
I hope this helps same time for other people looking for an app that is legit and not garbage like most of the ones available on the app stores.
Leave a message if it works for you with your device model so other will know if it’s compatible with their device.