You need few solution to get going for online training:
1. Your client would want to schedule appointment online.
For this you can use BookFresh (http://www.bookfresh.com/) or any other online appointment software. Just search for “online appointment software” on Google and you will get ton of options. Pick one that best suits your need. Make sure to pick one that integrate well with your website.
2. For video conferencing I would use Google hangout or Skype.
3. And last you need a solution that will let you manage clients. A program that would let you build workout program for them, review their daily activities, take assessments, measure their progress etc. There are fe solutions out there. We are building an iPad, IPhone, Android solution for both Personal Trainers and clients at TrainerFu (http://www.trainerfu.com)
DISCLAIMER: I am the founder of TrainerFu
Let me know if you have more questions.