your question itself has the answer… you say …
“Im thinking to keep an anti lost app in system partition….” and also know that..
….”and it’s can only be done with root access..”
read these do sentences again… you will get your answer…
also read this article
to get a rough idea of what its all about….
in simple words… to install apps in the SYSTEM PARTITION you will surely NEED A ROOTED PHONE..
also go through this stackoverflow question to clear your doubts of apps in the system partition after hard reset of the phone..
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solved How to make an anti lost app run even after phone hard reset?