NO SD Content Message

If I do not want to have a separate SD stream, only an HD stream for my published channel how do I display a screen when SDTV mode is detected that informs the user the channel is only compatible with HDTVs?

I know that I can get the mode the device is in by using the roDeviceInfo component, specifically the GetDisplayType() method but what should I do next to make this message appear for SDTV users?