SIGN LANGUAGE!!!! Get a baby sign language book and teach him and the family the basics. Say the word and sign the word and when possible show him an object for that word at the same time. For example, say drink, sign drink and then give him a cup with a drink in it. You could even have a drink. It works and you will be surprised at how fast he will learn and use the signs.
My 7yo started talking at 9 months and by 1 year had 40+ words she used all the time. 1 week after her 1st birthday she STOPPED talking completely!!! I freaked out when she didn't start talking again a week later. The Dr. assured me she was fine and don't worry until she turned 2. However in the mean time we needed to comunicate and I was sick of her grunting expecially since she use to talk. I taught her some sign language and it worked wonders. She even came up with some "signs" of her own that we all used and understood. I also taught the grandparents, family and friends the signs she used the most. She didn't start talking until she was 2 with speech therapy. She did catch up and pass the "norms" for her age 9 months later and now I want to know where is the OFF button! :) The speech therapist said she was learning so fast that her brain could not keep up with both the learning and the language and something had to stop for a while. She understood everything and when she did start talking again she knew the words to use.
If you are really concerned that there is a problem see your pediatrician and they can refer you to a speech pathologist. They can easily evaluate your son and see if it is a physical thing making him not talk or a choice or if his brain needs time to catch up (like my daughters did).
The tantrums can be helped with the sign language. It has worked for us and even the 2yo I taught basic signs around 9 months of age to help with the frustation and get her needs. She still uses them and talks a mile a minute!
Once the talking starts you may hope for an OFF button (there isn't one I've looked for one with both my girls!) A.