Looking for a door bell then do check this Digoo DG SD10 self powered door bell. You can easily install this door bell and there is no need to install extra cables, plus the door bell that you will install outside the home / office is water proof (IP44) and self powering.
Planning to invest in a security camera but backed out because of the price, well you can get the Digoo DG-M1Q mini WiFi Night Vision Security IP camera installed for just Rs. 1,300. Check this review, to know more.