Selectable Objects? Android tap

How would i make a selectable object in unity for android? I want to be able to tap an object and then assign a visual indicator to say it is selected. What is the best way to go about this?

My current setup is that i have the camera on a scene pointing down towards the "board" and i want to select objects.

I intend to tap on meshes of objects to try and select them. I brainstormed that i could draw a circle for each object and if my "touch.position" is within that circle (using a circle area equation) i would do my action. I would also need to find the origin of each model (since each mesh isn't exactly in center) and center the circle and change its radius so it barely goes outside of the bounds of the model. How would i detect the dimensions of the model?

Wouldn't this be very intensive if i have a lot of objects? What is a better way and would somebody be able to give a code example or a link to this kind of problem if it is mentioned elsewhere?