Mum concerned as husband keeps tracking their daughter on his phone

We all have concerns over our children's safety.

From when they're tiny babies to grown up adults, there's that parental instinct that will make us always want to keep an eye on them. However, there comes a point in life when you have to let go and let them live their own lives. You need to trust that you brought them up well, and they will stay safe when they're out of your care. That's why this mum is concerned as her husband keeps track of his daughter's phone... constantly. She said:

"If she goes out, it's every 15 minutes he's tracking her. I'm not too sure how to address this, thanks."

Many mums asked in the comments how old their daughter was, to which the mum replied: 18-years-old. With that, this is what the mothers had to say:

"She’s an adult. She can do what he wants and he must respect that. Is there anything your daughter can do on her phone to stop him tracking her?" "OMG I thought you were going to say 12 or 13, in which case I think would be fine. 18, no way." "18? So an adult? Put a stop to that asap! Ridiculous man." "How weird and horribly controlling. Please tell her ASAP."

What would you do in this situation?