You're confusing WhatsApp with snapchat, two totally different apps that have little in common aside from using the internet.
WhatsApp is free text and group-chat done right. Snapchat is ephemeral pics and recently they've added text and and video (also self deleting). It's possible that Google could've bought Honeywell but not at the price they paid for Nest ($3 Bil) but it would've been pointless, google isn't interested in getting into the low-grade thermostat market, they want to be part of the "collecting info about you from devices you put in your home" market, so even though nest's first product was a thermostat, that's just incidental in Google's overall plans for the company.
WhatsApp is free text and group-chat done right. Snapchat is ephemeral pics and recently they've added text and and video (also self deleting). It's possible that Google could've bought Honeywell but not at the price they paid for Nest ($3 Bil) but it would've been pointless, google isn't interested in getting into the low-grade thermostat market, they want to be part of the "collecting info about you from devices you put in your home" market, so even though nest's first product was a thermostat, that's just incidental in Google's overall plans for the company.