simple DIY door intercom

mrs_baggins

I am living by myself and to make me feel safer I would like to insall a simple intercom on my front door so I can ask who is there and so chose not to physically open the door unless I choose to do so. I have had a quick search on the net and there are phone types which would not be suitable. The door is external (obviously!) but is in a porch type area open to the elemnts but which would rarely get direct rain contact. I was thinking of a simple push button type on the outside with a simlar thing inside-preferably wire free but I am probably asking too much here. Has anyone any knowledge of this type of thing who may be able to give pro's and con's? thanks