How to force an application to stay open?

[EkSeS]

I have seen apps like Lookout, JuiceDefender, and MagicJack run in the background indefinitely, unless force closed by a user directly through the task manager. (And even then, in Gingerbread, it wouldn't close unless you browsed to the application that was running under "Downloaded Apps" in the settings and force closed it once you were at the menu where you have options to manage the app like "Clear Memory" and "Force Close".I am wondering how this is accomplished? I need to do something similar for an app of mine but I don't know how to avoid the Android OS's automatic task killing.. And don't say it's not possible because if that were true, JuiceDefender, MagicJack, and Lookout would not work.