Default [Req] doube click home button, launches last app used

[peteo]

Idea: your running an app like mobilechat. You then launch mail to check out an email. Now you want to go back to mobile chat. Right now you have to click the home button, scroll over to mobile chat and click on it. Would be cool if an app could run in the back ground that would record the last run app, and then a double click of the home button would launch that last app used or even better, a triple click of the home button would bring up a popup showing icons of last 4 apps ran and then you can click on which one you would like to run.

[jakecigar]

do you have any idea where the 'last run app' is kept? is there a log I've never seen?