Locks- AFAIK locking and unlocking doors is fine. Though some folks tie their keychains to belt loops or such due to sabbath laws.
AFAIK automatic timers are fine. Motion sensors would not be accepable as the light would activate as a direct and predictable result of your action.
The low tech solution of a 'shabbas goy, a nonJew who does things for you on the sabbath, has limits. If you directly ask them to do work (EG Could ya maybe turn on the light?) you’ve broken the rules about work. If you indirectly suggest that they do something (EG walking into a dark room, sitting down and saying "I think I’ll sit here and read for a while) you haven’t broken the rules.
Thank you very much for the compliment, but I’m no rabbi. Zev, so far as I know, isn’t a rabbi either, but he does know Hebrew and is very knowledable about Judaism, and halacha(Jewish law). C M Keller and a few other’s who I’m probably forgetting are also excellent at providing answers to all your Judiaca questions.
No, you misunderstand. The point is not that one can do work because the button is pressed. The act of pressing the button is “work.” (I put work in quotation marks because it is a misleading translation of melacha). By pressing the button, the person is completing an electrical circuit, forbidden under he melacha of boneh, building.
There is no reason to forbid ordinary locks and doorknobs. OTOH, electronic keycards are a problem.
DocCathode’s comment was to address a different problem. One of the melachos of Shabbos is carrying from a public domain to a private one. As such, one cannot carry one’s keys outside. However, the laws of carrying do not extend to one’s clothes (i.e. one can wear his/her clothing in the street, we’re not required to walk around naked 
). What many people do is form their key into the buckle of their belt, making the key a necessary component of the belt (you cannot otherwise close it). Since it is now an integral part of an article of clothing that he is wearing, an Orthodox Jew can wear his key out in the street on the Sabbath.
Yes, you can have a timer turn your lights on and off.
Zev Steinhardt
Part of me is saying, “Gee, I gotta learn more about this,” but another part is saying, “Why? You’re a Gentile so the rules don’t count for you and your one current customer who is an Israeli national seems to be either Reformed or unobservant.” “But think of the services we could offer!” “When you are in sales you can worry about the services you offer. You’re a glorified draftsman.”
Thanks for your help, guys. I know where to find you when I need more.