Let the hive mind of Engadget get that for you.
"We need a digital camera that can be switched on and fire off that first shot fast. It's not a commonly tracked statistic on any review site, and nobody seems to have this information for every camera. We were hoping other readers could inform us as to what small digital cameras can fire off their first pics in under a second (ideally under half a second). It needs to be small, but mostly, just really quick in operation. Thanks!"
I don't think the Kindle has the hardware specs to replace other handheld devices, and I would think that Gmail or Twitter apps wouldn't change the game.
The Kindle is for reading ebooks and developers should focus in improving the reading experience. The Nook is one step ahead thanks to its book lending feature, I believe that the Kindle Store would benefit from an Ebookcrossing App that could use GPS, or some app that would let users share ebooks or put them at stake in literature quizzes or comps.
I wrote a blog post describing these ideas, please let me know what Kindle App you'd like to see on http://www.bealoud.com/technology/kindle-development-kit/ :)