JACKSONVILLE, Fla. -

Imagine finding the man or woman of your dreams by GPS.  It's online dating, but on the next level.  Singles can now download smartphone apps to meet people instantly.  It's something Channel 4 Crime and Safety Expert Ken Jefferson worries about.

Sam Hyde met his fiancée, Nina using a GPS-based dating app.

“I was a little skeptical at first, I thought you know, this is, jeez this is going to tell people where I am,” explained Hyde.

But when he "checked in" through his GPS app, he found out Nina was standing in line at the same place he was.  They messaged to meet up.

“We just locked eyes and it was love at first site; love at first text,” he said.

So how many others are finding love the smartphone way? Our survey of major GPS dating app providers found the trend is taking off.

"Singles Around Me" says approximately 20,000 singles are installing the app each week.  "Okcupid" says one million of its three million use the GPS features.  And "How About We" estimates that about one in four of its online daters are now incorporating location-based dating into their search for a soul mate.

“It’s revolutionizing the way people are using their phones in order to meet people in the real world,” said Aaron Schildkrout, co-founder of "How About We."

Each app works a little differently.  When you check in on some, your profile and general location are automatically published to other singles nearby who can message you if they want to meet.  Certain apps reveal your exact location down to the street corner.  It's something that concerns Jefferson, a former sex crimes detective with the Jacksonville Sheriff's office.

"It can be an open invitation to stalkers.  It can be an open invitation to sexual offenders, pretending to be someone else for the sake of meeting other people," warned Jefferson.

Hyde said he had a frightening experience himself when a man posed as a woman to lure him into one meeting.

"I could very, you know, very easily have been in danger," Hyde admitted.

"One of the biggest problems with GPS dating is the immediacy of it," said Alan Rosenthal, author of the book "Safer Online Dating."

Rosenthal says in regular online dating, you have time to exchange emails or talk on the phone before you actually meet.  But with GPS, he says you could be face to face in minutes.

"You have no time to vet them or even to think about what your actions, your interactions or the ramifications are going to be," Rosenthal added.

Just this year, in three separate cases, three teens in Ohio, Wisconsin and California were sexually assaulted when they met men posing as teens on the GPS app "Skout."  As a result, "Skout" confirmed it made changes to its teen site, including removing location technology.  (Read more about the changes here.)

"Meet Moi," which sends profiles of people in your general location said, "Nothing is more important to us than user safety," and says, "We never share a user's exact location."

"Singles Around Me" says the app has, "privacy options that allow them to turn off their location GPS and or to hide their profile."

"How About We" says it's, "had no problems."

"I would advise women to just meet people the old fashion way versus the new technology that's out right now," said Jefferson.