Here's the game - in order to be useful for Photographic use the laptop should have an IPS screen. AFAIK the only Apple "laptop" with such is the iPad. Google on "ips laptops", I did and found that HP may have one.
And also be aware that if one decides to use a laptop with the much more common TN screen it will still probably be inferior to similar desktop monitors, because the backlight has a limited spectrum due to power consumption factors. I've calibrated/profiled several over the years and have never seen one that was other than marginally useful.
Richard Southworth