I have been happy user of the Android App called Google Opinion Rewards for about about 2 years. During this time, I've earned about $40. And I'll be the first to admit that $40 isn't anything to retire over, but it is the perfect amount to spend on the occassional paid app on the Google Play Store.
How Google Opinion Rewards Work? The first step is to download the Google Opinion Rewards application from the Google Play store. Once the application is installed and fully setup, you're ready to go. Google Opinion Rewards will send you a notification when a survey is available.
On average, I receive a Google Survey once every couple of weeks. It's a standard notification via the Android notification system. No noises or pop ups. Once I get the notification, I generally take the survey immediately, due to the fact it takes no time at all.
The Google Surveys are generally 3-4 questions long. They don't always pay anything, but I guess they would pay 90% of the time. Sometimes it's only 10 cents, but can sometimes be as high as $1. In my opinion, these stats are where Google Survey's shine against other web browser-based surveys. Google Surveys pay at a higher percentage of the time, but at a similar pay rate, but with much fewer questions.