This Digital Peephole viewer has a wider viewing screen, designed to fit into the existing fish-eyed optical peephole so you don’t have to make another hole to host this digital device. According to the merchant, the installation progress with take as much as five minutes only. So I guess it’s pretty easy to install.
The Digital Peephole viewer require you to throw in 2 AA batteries in exchange for 1,700 views. Pretty reasonable, just make sure you are going to use a rechargeable battery to safe the environment from hazardous alkaline.
If you want one for your door, it will cost you about $159.95 on Australian BoldTechnology.