We have cctv installed by a local firm. MIL house is quite isolated so there are cameras both front and back of the house. An alert is sent each time the doorbell is used so we can see who is calling and when. We had the option to add in an infra red alert if anyone came through the gate but we have not set that up. The cameras inside the house are just in her hallway and kitchen (where she spends most of her time). We have found this sufficient so far as we can see what is happening when carers or other visitors call. The system works with a telephone app and we can watch live if need be or review from midnight the same day on our phones if there are any concerns. Basic broadband is not sufficient to use these products - we had to upgrade to fibre broadband to get decent video and picture quality.
MIL agreed to CCTV and there are warning signs ( as required by law) that it is in operation. Sometimes she forgets, but others she sticks her tongue out at the camera if she is bored.
Our main problem was MIL's obsession with economy - the cctv hard drive had to be moved to the loft so she couldn't turn it off and the router was put in a rarely used room. If you PWD also constantly switches things off there are boxes that can be bought from online suppliers ( we could not use them because of the sockets position unfortunately)
Locally the carephone system is very useful - for a small weekly rental there is a pendant or bracelet with an alarm to press to call for help - the staff monitoring the system can then talk to the PWD through the phone line. There are a lot of additional extras that can be added to this as the PWD deteriorates - at the moment my MIL has a pebble device - i.e. GPS tracker that will alert if she is going into or out of designated areas. It can also be set to show speed - with my MIL who also has leukaemia it gives us a heads up is she is consistently walking slower when out of the house that her health is deteriorating again - this helps when talking to the Dr if I'm worried between clinic visits. When MIL started wandering at night the social worker suggested adding in a pressure pad which tells us when she gets out of bed or an alert to notify us if she is going out. It seems a very flexible system and to buy these devices separately would be quite costly.