Saw this article (via Lifehacker) today and loved it. I HATE those little mobile email signatures that excuse poor spelling and grammar, due to someone being mobile. Let alone the annoying taglines that advertise for the particular device and carrier.
In longhand, I think they say “I know there may be typos or I may have been a bit terse, but gimme some credit. I’m typing this on 5mm keys with my thumbs while waiting for my sushi, so be happy I triaged your email to be important enough to respond to right away instead of making you wait until tomorrow when it might get lost in my email pile. Gotta go … mmm, this food looks delicious …”
For a while now, I’ve been using this as my mobile signature. It may be equally annoying, but it makes me laugh and I’ve amused a few other people along the way as well.

Even if this signature is just as clowny, it at least serves as a good reminder to me, each time I type an email on my mobile device, to make damn sure that I keep it tight with the grammar and spelling. Or at least as tight as I would keep it when writing in my normal email client.