Default [Q] Voice controlled home automation

Hi,

I am looking at installing a home automation system in a clients house using a Bitwise controller. I was thinking about installing android tablets as an in-wall solution via WiFi rather than expensive light switches (Rako, Lutron, etc.) and multi-room controllers, as you seem to be able to pick up 7" tablets quite cheap. Stairs will still have standard switches.
I am aware of systems such as Crestron and AMX (we already install AMX) but I think there is a cheaper way to achieve this.
I understand they aren't going to be the best, but all they will be doing is running a Bitwise GUI designed for android tablets, so very little load.
I will have to make various changes to settings such as auto sleep times, wake up screens, etc. which I will address in a separate post. What I was looking for from the thread was to see how I can harness the voice control, which brings two questions.

The first is what is the typical range of the mic built in to the tablets and is there any way to enhance this?
The second is whether there is an app that provides voice control to something like the Bitwise BC1 controller, or am I trying to achieve something that isn't particularly easy?

I would be grateful for any guidance.

Craig