Switching between opened applications.

Hi.
Is any simple method to switch between applications, which are in background?
I know how to create a script to manage a "Home button". It checks if some of defined applications are running, adds them to the carousel, shows running apps and chooses app which we want on foreground. Somewhat like alt+tab in many OS. If none of defined apps are running, "Home" acts generally. However I don't know how to put app on foreground. I suppose there are some system events but which? Or is it at all possible?

Thanks in advance.