Hawkinson's timing was good. Although home automation has been around for decades, it's still far from mainstream. At the same time that SmartThings launched, Nest Labs, a "smart thermostat" created by former Apple engineers Tony Fadell and Matt Rogers, was hitting the market.
The intentions for this experiment are probably to help increase engagement. One could even argue that for content Twitter deems to be "breaking news," putting important tweets from the accounts a person's Twitter friends follow into that person's main timeline could be valuable.