Just before leaving work you use your smartphone to turn on the washing machine and the air conditioning and when you get home the interior is comfortable and the washing is ready to hang out. It sounds like a vision of the future, but with the right smartphone accessories, it's actually possible today.
From networked smoke detectors and app-controlled air-conditioning or heating thermostats to smart lighting, there's already a number of practical solutions on the market. But how do they actually work?
"There is a central control unit that communicates with each piece of equipment," explains Falko Hansen from German telecommunications-advice website teltarif.de. This usually happens wirelessly once the user has set things up via a smartphone app.
Using the smartphone, lights can be turned on and off, sensors can warn of windows that have been left open and a video camera over the front door can send an alert to the phone when someone is at the door.
Intelligent lights, smart windows and networked surveillance cameras are at their most effective when they work together, says Andreas Stumptner from Video magazine.
He says the technology is most useful "in combination with programming of absence scenarios that increase burglary protection or combined with apps with geo-fence functions which make it possible for the lights to automatically turn on when you come home."
Lights that detect motion may also help deter burglars. Networked cameras, motion detectors and window sensors warn when unauthorised persons enter the house. As an alternative to an expensive alarm system, smart home elements can help to not only make the house more livable in but also safer.
"In general, smart home applications that enhance security, reduce energy consumption for air-con or heating, or save money and which can also be controlled while you are out and about are particularly useful," says Stumptner.
Popular solutions are IP or wireless cameras which you can use to make sure that everything is ok at home when you're out. Similarly there are door and window sensors that send a message to your phone if, for example, their status of open or closed changes.
Smart lighting products include Belkin's WeMo, Hue from Philips or Lightyfy from Osram.
Networked weather stations with rain sensors and wind meters are also useful for homeowners. For example, with the right equipment you can close outer shutters if a storm is approaching, even if you're not at home.
Technology can also be used to trace energy guzzlers in the household.
"Smart outlets measure current and can display consumption data on the smartphone," says Tobias Arns from German IT association Bitkom. The energy consumption of older devices can be checked and a decision made over whether to upgrade.
So what are the most useful applications? Smart home enthusiast Stumptner recommends heating thermostats and controllers, shutters that react to the weather, as well as security applications such as smoke detectors, sensors and motion detectors.
He also recommends lighting and electronic controls that can be operated not only by app but also by keystroke or voice control, because "no-one has their smartphone with them at all times in the home."
All the devices need to function in a stable way and be linked with each other via open radio standards. "The main thing is that they are easy to install and easy to understand," says Stumptner.