Project Tango, Chromecast? Money also through Google apps, email and Android
Chromecast has sold 30 mio units since it was launched 4 years ago. Whereas that might be a lot for you and me if we launched a company, it's very little for Google.
If it had been an independent company selling 30 million units in 4 years for maybe $10-15 a piece to the stores, making maybe $5-10 per unit, you would likely never have heard of them. In 4 years Chromecast has probably made less revenue for Google than the ads make per day.