My Blackberry phone and Playbook have a micro HDMI output.
This is very practical, so you can display the screen on any computer or TV screen.
If you use a Bluetooth mouse or keyboard, you can make your phone handy like a laptop.
This is very useful when travelling to make a presentation during a meeting.
Also some hotel provide a TV with an HDMI plug, so you can watch your own movies
or YouTube movies on a big screen.
I wish other phones provide this capability too.
I noticed that most of the GPS LCD display for cars, provide an extra plug for external output,
in general used to connect a rear camera when doing backup, but its a yellow RCA plug.
However, you can easily find an HDMI to RCA plug.