I don’t know if you are going to find one with the px to rem, sounds like a great feature request for one of the existing plugins, but one tool that looks like it has the values on the x/y axis is “Designer Tools”. You can check them out…
I have not used it myself, but it seems to have some really great reviews.
Did you know: Google developer tools has its own built in rulers. Not as useful as perhaps some of these plugins, but if you go to developer tools > settings > preferences there is a checkbox “Show rulers”. Then when you inspect an item or select it through the “Elements” tab, it will show the rulers across the top and side with the x/y marks. Might be worth a try and see if that is good enough.
But as far as the px to rem, well like I said I don’t know if that is a feature of any of the extensions. Usually if you are measuring you want px and obviously rem is in relation to the default browser size and so could be different for all sorts of browsers. Rem you want to be looking at the ratio more than something like a definitive unit like px.
I hope this helps!