What do you call a person addicted to the computer?
The slang word for a person always on the computer is "computer geek or nerd."
If they are good at it, you can call them an artist. There doesn't seem to be a name for people who are addicted to painting. There are people who are addicted to painting specific things, such as people addicted to applying nail polish. These things would fall more into compulsions, since they are not dangerous activities and don't directly harm others. Then there are people addicted to inhaling paint. Those would be huffers and…
Sitting too much and not getting enough exercise. Strain on the eyes. Social problems because a person who is addicted with computer games doesn't socialize well and is more interested about getting back to their computer than making friends or having fun. The fun IS in their computer games. Eating junk food because usually people addicted to the computer won't eat meals on time.
There's currently no scientific specific term for a person addicted to cell phones. However, the common term used today would be something along the lines of a "nomophobic." Nomophobia is the term for someone who's afraid of not being on their cell phone given the shortening of "nomo" (no mobile phone phobia).