This looks cool! Some random questions/suggestions from a bystander:
I agree. I'd use such an extension... if I had a mobile phone... which I
don't. :o)
* I would be happier with two separate variables for the RFC 2822
"display name" and the "address". Having both the name and the mail
address would fill up my entire cell phone display. Maybe keep
$from$ as is, and add $from-address$ and $from-name$.
I'd also like to see this addition. This is the kind of thing that irritates
you every single time you use a feature, and wish someone had implemented.
It's like all those computer games with 60 second movies between levels that
you watch about 200 times and end up wishing it wasn't there in the first place!
I recon you are most interested in $from-name$ and $subject$ and slightly
interested in $from-address$. Mobile phones make for crappy mail clients at
the moment, so they aren't all that much use for lots of $text$, but I suppose
you would typically use $text$ so that you could read the message if you wanted
to.
Nigel