Always the unnecessary hi-tech solution
What's wrong with the traditional way of stalking? You sneak up to the stalkees home at night, fill their bedroom with sleepy-gas of some sort, then while they're unconscious you get your tame struck-off-alcoholic-doctor to operate to insert a small radio device under their skin (where they won't notice) and then you can track them for months (or until the battery goes flat).
Who needs leaky software? And this method works without getting the stalkee to use a 'dating app' (whatever one of those is)