In the Digital Age, the postman never needs to ring twice. That's because of inventions like the "GSM Doorbell" from Dutch start-up Waleli, which will automatically call your mobile phone if you're not immediately available to greet visitors--and you can unlock the door remotely just by punching in a designated number.
As Gearlog points out, it's really more of a smart system that includes an intercom, electronic lock and SIM card for your handset. Waleli says the system, which works with any phone on an international GSM network, has already been on the market in the Netherlands and may be released in other countries this year.
The company has seen a variety of uses for its product and says hospitals are testing it for use with homebound patients. But we envision more common situations, such as letting in the kids when they're home from school. This could render the term "latchkey children" entirely obsolete.