Robin Hanson talks about the economics of the Singularity where economic growth rates accelerate 60-250 times. This site has talked about Singularity Lite where the 2-3 times increase in economic growth rate from the early (1730) to late (1900s) part of the industrial revolution is repeated.
If the economic impacts of a Singularity are correct then a clear sign of a Singularity would be if world economic growth rates goes to current China levels of growth or higher. The difference between Singularity lite and a full blown Singularity would be if the majority of the world economy is more than doubling every year.
If 1996-2000 rates of change for the Internet industry speed hits and radically transforms education and healthcare, then you are probably in a Singularity.
If you have a device that guides you through the first day of your new job like Morpheus telling Neo which turns to make in the first Matrix movie then you are probably in a world undergoing a technological Singularity. If the device is providing those instructions via a direct brain-machine interface then you are definitely in a technological Singularity.
Note: Emotiv already is selling inexpensive brain computer interfaces for use with video games.
Emotiv graphic. The device on the woman's head is a real brain computer interface. The projected image is not an actual current interaction.
If over 90% of the businesses and industries this year did not exist last year then you are probably in a technological Singularity.
Vernor Vinge indicated :
The consequences of creating human-level artificial intelligence would be profound, but it would still be explainable to present-day humans like you and me. But what happens a year or two after that? The best answer to the question, “Will computers ever be as smart as humans?” is probably “Yes, but only briefly.”
If the world's energy and transportation infrastructure is being replaced multiple times per year with radically improved technology then you are deep into a technological Singularity or experiencing a hard takeoff.
If every quarter or week, you have to change out your mind machine interface device for one that is over ten times faster in order to "stay competitive" you are in a technological Singularity.
Add your less subtle signs of a Singularity in the comments.
Contact lens displays
Displays in glasses exist now.
Cheap brain wave sensors
Somewhat related: A robot performed brain surgery for the first time.
Microsoft captcha's broken. Captcha's are the letter graphics that are designed to be human but not machine readable. Advancing machine progress can be measured by the frequency with which the "test for humanness" must be changed.