The wanna-get-fit mom
If your mom needs a little inspiration to get moving, she could enjoy counting. Tracking your steps is a great motivator and gives a concrete goal. There's plenty of options, from the simple pedometers that cost a few dollars to the more advanced $100+ gadgets that align with online diet and exercise programs.
Whatever you choose, if you find one for yourself you and your mom can check in on one another to make sure your both getting those 30 minutes of cancer-protective activity a day.