Overlay peak value on video

[Paul Barber]

Hello.

What do you think would be the best way to write an element that makes 
some measurement on the video buffer (say the peak RGB values) and then 
overlays that measurement onto the video itself?

Making the measurement is no problem. I have used the template filter 
plugin, access the buffer and detect the peak values in the video chain 
function.
I am also aware of the textoverlay element which will overlay static 
text or via the text sink .
Can I make an element that will act as a text src for the textoverlay 
text sink?
Can I push text out on a text src pad from within the video chain function?
Or is there a better way?
Cheers,
Paul.