I am desperately trying not to get flabby arms like my mother! I do try to do lots of things with my arms, carrying heavy shopping bags and keeping a tension in my arms, rigourous gardening etc. However, a good way to work the triceps, whilst watch TV

, is to get a little stool, or even the coffee table, sit on the edge of it, put you hands either side of your hips with your fingers over hanging the edge. Place your feet about 1m away from the table flat on the floor and slightly apart. Take the weight on your arms/hands and slip you bum off the table. Keeping your weight on you arms (and a little bit on your legs), bend your arms so you dip below the table edge. Don't go too far cos you could strain your triceps but take it down so you remain comfortable. Using your arms, raise your body up again and repeat, down and up, until you can't take any more. Have a rest.....then repeat! as much as you want!
Remember to stretch your triceps out again when you've finished!
Hope this helps!