Nothing prevents a phonbe manufacturer putting a video-out interface to their phone, if they wish.
If you also get a TV manufacturer to cooperate, it could also be done through an USB cable or wirelessly with Bluetooth or WLAN (both devices would, of course, have to support the same mechanism).
Something like that may come out as a standard (depending on what kind of use cases they work on) through the DLNA, Digital Living Network Alliance (http://www.dlna.org/) & especially their Mobile/Handheld Subcommittee.
The composite video connection can be hooked up to your TV.
There are also wireless adapters for composite video.
So basically if your 3G phone can show your caller participant on the phone screen, you can get it to your TV with this Camero device.
I need to transmit key presses from a Nokia 6820 phone (Series 40) to a computer for testing purposes. This would have to emulate a local keyboard, so a Bluetooth HID profile (used by Bluetooth keyboards) would be suitable.