Back of JVC's RS4910 Projector (and RS49, X500R)
Right below the two HDMI inputs, is a standard RS232 Serial port with the usual DB9 connector.
The DIN connector for the optional 3D RF emitter is below the HDMI inputs. The device plugs in and "points" down. To its right is a small jack for a 12 volt screen trigger.
That's it. What's not here are some low res inputs - composite video, and S-video, but we're definitely seeing more manufacturers no longer including one or both those, especially on higher end projector models.
It would have been nice if one of the HDMI inputs was configured to support MHL, which would have allowed some internet smarts to be added, such as a Roku stick, or directly interfacing some android based phones and tablets!
We are starting to see HDMI with MHL in some home projectors, although mostly on the lower end of things. It's catching on rather quickly, as MHL has many benefits. My Roku stick, for example would have allowed me to do Netflix directly, as well as many other online services. But to take full advantage of MHL, audio comes into play, and the JVC has no speakers, nor a way to pass on any audio signal to an outboard sound system. Next generation? We shall see.