The computer and cell phone are PRIVELEDGES that you get for completion of you chores. No completion, no computer or phone. It is that simple. If you go to work, does your boss have to remind you everyday to do the the work you were hired to do? What would happen if he did? Would you keep your job. I would suggest that you and your husband get on the same page, come up with your expectations and the date to start enforcement. Then have a talk with him. Let him know what the new rules are, then watch and see and discipline accordingly. The computer can be locked in the trunk of a car so he can't use it, or just the keyboard. same with the cell phone. contrary to popular belief he can live without it.
He should not need to be reminded. He is lazy and knows that yuou will not do anything. If he thought you were serious about something he might. But you have taught him that you only expect him to do something when you tell him or get mad at him. And you didn't mention discipline when he didn't do chores or mow the lawn. So are there any?
You are not asking to much, you just have poor follow though, no consistency or no discipline. You also said you were a perfectionist, but didn't say you required him to do it YOUR way. you just wanted it done. It is natural for his age to act this way, but that doesn't mean you have to settle for it. After all if everyone jumped off a cliff.....
it is your house, so make the rules what you want. maybe one night or day as family time. games, shopping, bowling, miniature golf, fishing, hiking, etc. and then let him have some alone time with his friends.
good luck.
laur