You have to remember that you and your app are a "guest" on the Android system, at the discretion of the "Android Overlord". Your app is no more important than the latest "Flappy Bird" clone. Unless...
You will probably need a rooted phone, with super user installed. I have used the following in scripts, but never through B4A, so there may be an Android/Java interface as well, I just haven't checked.
Look into setting your OOM value and Renicing your process id; careful, the values are in reverse order ie lower means higher... for at least one of them and also go into -ve for OOM I think. I previously had a phone with only 512mb ram and setting these values to the extreme did a pretty good job of limiting Androids ability to randomly kill processes. In my case, it would previously kill my background music player while I was using Navigation (Google Maps)
But even with the above, i don't think you will get around a "Force Stop" in Settings/Apps