Design HTML newsletter for/detect mobile devices

[Dave]

Are there any guidelines for designing HTML newsletters for mobile devices?
Our company is rolling out more and more of these devices.

Currently, we were going to offer users the option to sign up for a text
version (if they use mostly PDAs to read email) or HTML version if they work
mostly in the office.

I see there is a MailMessage.AlternateViews to show either text or html if
the email client is one or the other. My question is though, if they sign up
for HTML versions, is there a way to detect mobile device/email client to
render a scaled down HTML version or just force the the text version on the
device? But if they're in the office, still allow them to see the full HTML
if they happen to view it in Outlook 2007

Thanks