How can I remember to periodically check the minimap and resources?

I know two such tools. Both of them based on day 9 mental checklist idea:

• day 9 coacher that simply loops sounds
• sc2drill application. I recommend this one. It allows you to define independent notification loops for map / production /resources event. Plus this tool has "smart" mode ("score & notify" as I remember) to notify only when you stops to check you production buildings etc

There really isn't a kind of program that will monitor it for you.

It's simply something that you'll have to practice.

During the heat of battle it is difficult to manage these things. One of the things I did a few times was just to do a few practice games versus the AI and all I focused on was building units, checking supply, upgrading, etc. I rallied my buildings to the AI's base so they would keep getting killed. I kept a few units at home to make sure I didn't keep dying. It also helped my micro to try to survive with small armies.

Eventually it becomes part of your mental checklist and it will become part of your gameplay.