I have been trying to find a cable to send video from the EVO to my tv system in my GMC Envoy. Apparently since the HDMI signal is digital and the Composite RCA is analog you need and adapter similar to this to make it work.

Gefen Inc. - GefenTV HDMI to Composite Scaler

Then you would need the HDMI cord from the EVO to standard HDMI on the adapter and then composite RCA's between the adapter and the entertainment system/TV.

It does still appear that the EVO may not be able to send Sprint TV from the EVO out to an external display. Hopefully this is changed or untrue. Or, maybe rooting the phone can allow it if it won't output video out of the box. Anyway, if it can be done, it looks like we'll need something like this to make it work from digital to analog.