Android/iOS: Hiring a personal trainer for your workouts may have some benefits, but working out from home is still cheaper. Runtastic Results provides the best of both worlds with personalised workout routines on your phone.
The app, from the same developer as Lifehacker favourite running app Runtastic, will create a 12-week course based on your needs and goals. Much like a regular personal trainer, it doesn't come free, but it's no more expensive than Netflix. You can buy in for $13/month, or pay $65 up front for the year. That price puts it in the ballpark for most budgets while still giving you a financial incentive to not give up.
Runtastic Results [iTunes App Store]