Camera to take picture of lecture

After looking at some point and shoots, I'm more confused as ever so i'm posting this to get some suggestions on what to buy. I'm tryign to take lecture slides in a lecture hall. Here is my "ideal" camera. Can someone suggest some cameras I should look into? Thanks!

1. small (stealthy)
2. good amount of zoom (150mm + due to large lecture hall)
3. good battery life (last the whole day preferably)
4. AF lock
5. turn off LCD to save battery life
6. cheaper is better.