To keep an eye on something or someone is a common idiom which means that you are paying attention to something, or taking care of someone in order to protect them.
At the moment, I’m keeping my eye on an eBay advert for a beautiful juke box. I really, really, really want it, (seriously, you have no idea!) and although it’s as cheap as chips now, I imagine that all the other bidders are going to make it cost an arm and leg in the end. In addition, I’m keeping my eye on some ‘eye candy’ at my gym. Furthermore, every time my mate, Max, comes to stay with me, her mum always phones me to ask if I will keep an eye on her. I know, given that we are both practically claiming our pensions, I seriously doubt I have any control over her mischievous behaviour! However, it’s great that her mum thinks I’m the most sensible and responsible person out of us both. Truth be told, I am, because she’s a complete nutjob!
