I'm a running coach and would like to have Google Home tell clients their workouts & stats.
Yes, this is possible. I am an active stakeholder in an organisation that has developed high performing voice apps and is currently building fitness apps (skills) for Google Home and Amazon Alexa.
One of the easiest ways to start is from the following link:
There is a lot of nuance in this upcoming field of Voice Development. If you need further answers or would like a call then please connect with me.
Yes, it is possible. With the introduction of Actions platform from Google for developer, we can build apps to extend Google Assistant, which is the core of Google Home.