To me, that is a job for an Xposed module (Xposed requires root) named "App Settings".
Within that module, assign the app of interest as "Resident".
Then it will get assigned a higher priority (like a service) than most of your other apps.
In fact it will show up in the Running Services portion of your settings (rather than the cached processes portion).
I find two big uses of it:
1 - Apps that you want to be always running (like your pie control). For me it is Swipepad and Tasker. Swipepad and Tasker also provide a setting to provide an entry in the notification bar or notification pulldown shade to accomplish the same thing. But using App settings means you can accomplish this without cluttering up your notification areas.
2 - Apps that occasionlly get killed at a bad time when you put them in the background (by switching to another app), ,interrupting their function. For me it is google MyTracks and Navfree. MyTracks gets killed and stops recording my run or paddle... defeats the purpose. Navfree gets killed and stops giving me directions. Making them "resident" in app settings fixes this. What I have to remember is to go manually kill them after I'm done with the app (assuming I won't be using it again shortly). Otherwise they take up precious high-priority memory perpetually and unnecessarily. Note the distinction - there is usually not much reason to manually kill a "cached process" since Android can kill it when needed, but this is a good reason to kill an app that I myself promoted to a running service that Android will be very reluctant to kill.
It's pretty much the same thing I talked about here:
http://androidforums.com/threads/check-if-app-is-running.922076/
I gather there is some disdain for altering anything at all to do with memory / app management arising from the legitimate campaign against auto-task killers. I agree about auto-task killers, but this is not anywhere near the same thing. Think of it this way: a developer can give an app a service to make it higher priority. Sometimes that's justified, sometimes it's not. Either way because it has a service, it gets an advantage over all other apps without service (and without visibility such as notification). An unscrupulous developer (one who is not concerned with your resources) could add a service to his app simply to make his app load faster and stick around longer. Why should developers be the only ones with that power? It's my phone and I know my needs and I know the situations where the built-in priority system of android (combined with peculiarities of individuals apps) is not working quite the way I'd like...why not use App Settings "resident" in these situations. I have 400-500 apps on my phone, these are the only four that I assign as resident.
