Treadmill
Even with an RX, a treadmill can't be deducted. You MIGHT be able to use Flexible Spending Account $$$ if you have an RX, but that varies from company to company. The government just hasn't "gotten" it yet, but these things will EVENTUALLY be deductible if you can prove you use them.
I would suggest going to the gym and trying the machines there. Find something you like and then look for something similar. Treadmills - last time I looked - can run from $149 for cheapies to $3500 for top-of-the-line. Really just depends....do you want a Ford or a Cadillac? You can also ask the trainers at the gym. Ask what they'd buy id they were getting one for their personal use.
mpf