My kids are 15, 13, 11, and 8. The TV isn't a huge problem, we don't have cable but have a Roku to watch Netflix or Hulu occasionally. My problem is their computers/games. Their dad bought them laptops/Nintendo DS's, and especially my teens have become addicted to the pc. They want to be on it all day, especially now during the summer. It's driving me bananas.
We give each of the kids 30 minutes a day to be on the computer, wii, whatever. They can also earn time or lose time depending on what's going on. That seems to work pretty well. They've learned that once their time is up, it's up. If they complain or stay on after I've asked them to get off, the extra time that they use, comes off their time for the next day. It seems to work pretty well. That's not to say we don't occasionally have some arguments!
That sounds like a great idea, QueenoftheMeadow, and I wonder if birthjunkiemom tried it.
When I read the original post, I remembered when I was a teenager (not too long ago) and my Dad encouraged me to get off the couch and go outside. He took my brothers and I to the park to play soccer, and my Mom rode bikes with me to the state lakes outside my hometown sometimes. Also, Dad had a jetski that we took to the lakes, and occasionally we went to the public pool before it was turned into something else. For one summer I bought a YMCA membership, walked or biked there and back, and used the walking track and weights.
Also, since your 15-year-old will be old enough to start working before you know it (assuming 16-year-olds can work in your state like they could/can in my home state), you could encourage him or her to volunteer for you and your husband, and for other family members and neighbors - like raking leaves, taking out the trash, sweeping after dinner, washing the dishes, shoveling snow, etc.