Re: about the power of the 5mW laser
I have read that green lasers will do the job for daytime visibility.
For example, firearms can be equipped with laser sights, and they are almost always red. A disadvantage of a red laser sight is limited visibility in sunlight. A green laser sight is a solution to this problem because they are clear even at noon on a clear, haze-free day. The green laser sights are much more expensive, but I think that may be due to fragility. Red lasers seem to be cheap and durable, but the green ones seem to be more expensive and much more fragile.
Two of the manufacturers, if I recall, are Crimson Trace and Lasermax.