"I found myself more stressed and scoring worse in the real test in relation to the practice test. I knew it wasn't necessarily my nerves, I thought it was related to my time management," he told ABC News.
With the help of a tutor, Liss, who is now 19 and a sophomore at New York University, came up with some good tricks, including using an analog clock to monitor his time. But it wasn't perfect, and that's why he came up with what has now become the Testing Timer.
"It started as just an idea. I kept wishing that there was a watch like this out there. I decided I was going to go through with this and make a change for students like myself."
This week his company, Testing Timers, begins shipping the aTest Timer for ACT tests (the sTest Timer for the SAT is on the way). It might look like a regular digital watch, but it has settings tailored to the test, including preset times for the English, Math, Reading, Science and Writing sections.
"It is as simple as picking your section and starting the timer," Liss said. The watch shows the total time for that section, a countdown with the time remaining, and surrounding all that is a track of sorts. Like the readout on a treadmill or workout machine, it shows how far along in the test you are with a small blinking light. Liss said that students can easily see if they are behind or ahead.
The watch was also built with the restrictions of the ACT and the College Board (the company that distributes the SATs) in mind. The College Board and the ACT told ABC News that there are restrictions on some watches, but that because the Testing Timers don't vibrate, make noises or have any computing functionality they should be in the clear.
"Wrist watches, many of which have countdown timers on them, are allowed," Jason Baran, a spokesperson for the Educational Testing Service and the SATs, told ABC News.
"We can't comment on any particular brands, but there are a number of watch timers on the market, and students can wear a watch as long as it meets our requirements -- that is, it doesn't have cell phone capabilities and doesn't make noise (alarms are prohibited in the testing room)," Ed Colby, a spokesperson for ACT told, ABC News.
Liss said that the new wave of smart watches coming from companies like Pebble and Motorola are going to be restricted.
The $39.99 aTest started shipping this week and already Liss has sold a number to tutoring companies in his home town of Chicago. The SAT watches have just started to be manufactured in China and will ship soon.
But the young entrepreneur is thinking even bigger and hopes to work directly with the testing companies. "My goal is to work directly with them -- to allow students to rent them out the watches. I think it can help the overall wellbeing of the test."