Other than using Panel (which is excellent, BTW, especially for devices without a dedicated remote app) if you're using Android, I'd suggest checking out the new JRiver remote,
MO 4Media. It has one distinct advantage over JRemote/Gizmo/eos right now, which is gapless playback. It supports audio, videos and images. That and it's in active development with updates pushed out every so often. On its roadmap is Chromecast support, live TV support and Android TV support, which all would be great to see.
If you're using iOS, I'd suggest telling the author cncb that you'd like to see it ported to iOS. The more interested potential users, the better the chance of it getting ported to iOS.
You might want to also request that the streaming features (RP and RJ) are added too.