Well, my ds is only 19 months old, so I am also new to this tantrum thing, but I can give you my experiences so far. I try to let him check out anything that I possibly can. If there are only certain hours that your dh needs the cellphone on, then maybe let him check it out after hours. You could also try putting the keyguard feature on, and then he can check it out without pushing any buttons. That's what we do around here with our cellphones.
But if it's one of those things that he cannot play with, period, then around here we just keep explaining, redirecting, and empathizing with the tantrums. Example: Ds wants the knife. I explain to him that he cannot have the knife because it is sharp and he could hurt himself. He throws a fit. I try to substitute other items. If he's tired, this usually doesn't work. Then I remove him from the area of the item, explaining again why he can't have it, and then just hugging/holding/standing next to him, say something about how I understand how frustrating it must be to not be able to play with what you want to, I know you're angry, etc. etc. Sometimes I pick up and start playing with a toy he likes, to see if that will catch his interest. And then just let him have his fit. (I know this is not fun, I hate every moment of it.)
Even if he doesn't totally understand me now, at least I'm setting a precedent at how I would like to handle these things. But it seems like he is starting to understand when I say these things. It doesn't seem like there is a magical fix to every tantrum, and that they just need to learn that some things are not appropriate for them to play with. I just try to emphasize all the great things that he can have.