Helge and Kari Farsund, who live in Oslo, Norway, have been a couple for 50 years. Mr Farsund worked as an engineer, while his wife was an intensive-care nurse, at one point serving with the Red Cross in Rwanda, helping victims of the violent war in that country.
Three years ago, a more personal tragedy struck, when Mrs Farsund was diagnosed with Alzheimer's.
As the condition deteriorated, Mr Farsund began looking for a system that could help both of them live as normal a life as possible.
He stumbled across healthcare technology company Abilia, which has come up with just such a network.
At the centre of the system is a wall-mounted iPad-like device. The screen has Skype, which allows allows carers to regularly check in with patients.
It also has a planner for patients or carers to record up-coming events and provides spoken reminders about daily tasks, such as when they need to take medicine.
Some 1,000 people now have the system installed in their homes, and 25 of them, including the Farsunds, are testing the latest version, which combines the screen with wirelessly connected sensors.
The motion sensors know if you are in the room or open a door, and send out alarms, for instance if the stove is left on for more than 15 minutes or a person opens a door in the middle of the night.
The second is a particular issue in Oslo, where sub-zero winters mean some Alzheimer's patients are freezing to death.
"With this kind of system, it allows people to take care of themselves, which is the most important thing," says vice president Oystein Johnsen.
"It also saves the government money. In Norway it cost one million Norwegian krone per year [£100,000] to have someone in a home, this system costs 15,000 a year. That is a lot of money to save."
For him, any move to improve city life needs to begin with people.
"Smart cities are coming and they need to start with individuals in their own home," he says.
Mrs Farsund explained in Norwegian how the system has helped her.
"She says that she knows that she won't get better. The system helps to explain to her what is happening each day so she can look forward to events like birthdays or the club for retired nurses. It gives her something to look forward to," translates her husband.
For him, there is a more practical and poignant reason to have the system.
"Sometimes she asks me what is the meaning of life because she is missing so many things because of the illness," he says.
"I was afraid that her depression would lead her to jump over the balcony.
"With the sensors, I know that I will wake up if the door is opened and that allows me to sleep.
"I want to go to bed and not worry about her. This was the most important thing for me."
As governments begin to use technology to improve city life, the older generation should be top priority, says Intel futurist Steve Brown.
"We have an ageing population and a lot of old people are now living in our cities, so we need to start building technology that makes it easier for them," he says.
"We cannot build enough hospitals to deal with the ageing wave of people, so there has to be a rethink about how do you help them to live at home.
"It is possible now, just from people's movements and habits to detect, for example, the early signs of Alzheimer's."
At Manchester University, scientists have developed a "magic carpet", designed to detect and even predict, when old people fall at home.
The carpet is fitted with plastic optical fibres. The fibres bend when anyone treads on it and can map, in real time, their walking pattern.
Electronics at the edges of the carpet act as sensors and relay signals to a computer that can then be analysed to identify changes in walking behaviour or sudden falls.
For many starting to contemplate old age, the biggest fear is being put in a home, but often institutional care is the only way to ensure dementia patients are safe.
In Sussex, the police estimate that one in four missing person enquiries involves a dementia patient.
To save time and money, the county has funded a controversial global positioning system (GPS) tagging system for those with the condition.
The MindMe device can be worn around the neck or attached to a key ring and allows family and carers to keep track of relatives with dementia.
"Family and friends can go online and see where that person is. Those using it see it as a lifeline. It gives them newfound freedom and independence," says a council spokeswoman.
She says one woman used the system so that she could continue to walk her dog on her own. Then on one walk, she got lost.
"Her husband noticed via the system that she hadn't moved for 10 minutes and went to find her," the spokeswoman says.
"She was in an isolated field, stuck in mud. She may never have been found without the technology."
But critics have dubbed the scheme inhumane and questioned how people with dementia can properly give their consent to wearing such devices.
Sensor technology is increasingly being used in cities to provide hitherto unknown information about how traffic is flowing, where water pipes are leaking and how much rubbish is going in bins.
IBM is one of the leaders in providing such technology and it has recently made it clear that healthcare is one of its top smart-cities priorities.
In the Italian city of Bolzano, IBM worked with the council to install a network of sensors that monitored the homes of elderly citizens living alone, keeping an eye on temperatures, CO2 levels and water leaks.
A huge poster appeared on the streets of Dublin recently, featuring an old lady, spray paint in hand, scrawling the message: "I want to grow old at home."
When 90-year-old Mabel Gargan agreed to take part in the campaign, she had more than just granny graffiti on her mind.
She was also making a point that many will sympathise with - that a society that truly cares for its citizens will be one that allows them to have dignity in old age.
There is little doubt that most people, just like Mabel Gargan, would like to grow old at home.
City councils considering smart technologies would do well to listen to the message, says Andrew Hudson-Smith who heads up University College London's Centre for Advanced Spatial Analysis and sits on the Smarter London board.
"My mum had Alzheimer's and there were times when a smart device would have made all the difference," he says.
"Smart homes are not about internet-connected fridges, who wants that? But if sensors could tell me when my dad opened a fridge, I would know that he is OK."