Put in
Gila window tint in my front room. It definitely helped with the sun super-heating that room. You can't see in the window from the outside during the day (kind of creates an almost two-way mirror type situation). During the day and night though you can see out it just fine. No idea about how it affects plants.
And if you buy this, don't be a cheapskate like me and
buy the kit. I did the second half of the project with the kit and it was SO much easier.
Also, follow the directions exactly and have somebody to help you. Much easier with four hands as opposed to two.