Accuracy depends on putting your eye in the same place all the time. If you move your head around, the dot will move with you even if your 'gun hasn't. Unfortunately like most cool toys for big boys and girls, these need batteries. Most players who use sights end up with a reflective sight. I can't in good conscience suggest these to any one, and I'll tell you why.
Laser sights project a very bright beam of light in a very small area.
If it hits a person's eyes, they can be damaged. The beam enters the eye and is focussed in an even smaller area on the retina and burns it. Arc welders call this Eye Flash and have to wear very dark lenses to work. For this reason, lasers are banned on most fields. Laser pointers have even been banned in some school districts in Canada, and if you point one at someone's eyes here in Ontario, you can be charged with assault.