Originally Posted by jerofld
You should probably go to the police, anyways. They can subpoena your cellphone records to show where your cellphone has been. It's harder to say that you're a stalker if you keep to a certain pattern that doesn't deviate to follow this girl.
As for an app, nothing third party will be beyond scrutiny. The cell company's records would be more admissible.
That and credit card, debit card records. Especially since that might lead to security camera footage that proves you were elsewhere. Consider getting in the habit of making small transactions during the day at gas stations or other places you know have cameras. Or withdraw $5 from the atm at random points in the day.
And like others said, call the cops, and/or talk to a lawyer.