I thought I would share a few screen shots from my phone as to how much data and the battery the app has used over the last couple of days. I purposely didn't use the phone too much so I could see what effect it had on anything.
This is my general phone use.
Percentage of use.
DellVoice specific usage. The data sent and received numbers include two calls that lasted about 4 - 5 minutes each.
Overall my phone will last at least 2 days without doing too much on it, so I would expect it to last a day easily with my normal use. I was worried that the drain would be fairly high, but it seems not on my phone at least.