Think your kid's being bullied? Or sending sexts? Or dealing drugs? There's an app for that.
In the United States, nearly 80% of teenagers own mobile phones. About half of those are smartphones - with access to the internet, games, cameras and social media.
That worries many parents. And those fears are fuelling a growing number of so-called parent apps - to track what kids are doing online.
TeenSafe can work as a personal CIA spy for parents.
The company urges parents to tell their children they are being monitored, but the app can work covertly and show what kids are posting on social media as well as deleted texts and messages sent via popular apps such as Kik, WhatsApp and Snapchat.
"It's absolutely legal for a parent to do this discreetly," says TeenSafe's chief executive Rawdon Messenger.
"The real question is, 'Is it justified?' and those are moral decisions a parent has to make. What we believe is that when it comes to protecting your child from these things - privacy is trumped by protection."
Mr Messenger says he believes about half the families who use TeenSafe use it to spy on their kids.
TeenSafe operates in the United States, Canada, Australia and New Zealand, and is hoping to expand to the UK soon. Since it started in 2011, it says it has had 800,000 people sign up for the service.
Aside from tracking social media use and texting, other parent apps can actually monitor how fast someone is driving or moving in a vehicle as a passenger.
MamaBear offers that service, and co-founder Robyn Spoto says the app is used to link entire families and send alerts when someone is driving above the speed limit or has ventured outside a pre-determined boundary. It cannot be used covertly.
"Technology is your right-hand man to give you the information that you need so that you can have the right conversation," says Ms Spoto.
She adds that many families find it reassuring to get push notifications about their children's whereabouts.
Ms Spoto uses MamaBear for her parents and 10-year-old son, who does not have a phone but uses an iPod Touch.
But don't her own parents feel annoyed that their adult daughter gets push notifications every time they speed to work or come home at 01:00 from a party? Laughing, Ms Spoto says they're used to it.
"It's not like I'm creeping on them," she says, adding that she likes the assurance of knowing they got home safely.
Teenagers are typically better at using technology than their parents, and apps such as these can create a cat-and-mouse game of kids trying to avoid prying eyes.
But the parent apps are prepared - if your child does not call you back or turns the phone off, you can disable the phone so it only works to call mum or dad.
Some call them the "stalker apps", worrying that data gathered by smartphone spyware could be misused by suspicious spouses or mistrustful bosses.
And it seems the US authorities share these concerns.
Last year the FBI arrested a man for distributing an app called StealthGenie, which intercepted emails and texts as well as recorded phone calls.
Prosecutors highlighted that the software was marketed as being "undetectable" and suggested it was designed for "stalkers and domestic abusers".
In the first ever criminal conviction of its kind, Hammad Akbar was subsequently fined $500,000 (£332,840) after pleading guilty to advertising and selling the app.
Smartphone monitoring services are, however, legal to use in the US, so long as the software is installed on a device used by either the customer's:
- child - who must be under 18 years old
- employee - so long as the worker has given their consent and been told they are being monitored
Several available products highlight their restrictions in their small print, even if, occasionally, they also market their "cheating spouse"-catching potential.
"As far as the UK is concerned, the use of 'stalker apps' could very easily land you on the wrong side of the UK Data Protection Act 1998 and other applicable UK laws ," commented Vin Bange from the law firm Taylor Wessing.
"Domestic use is treated very differently to surveillance in the workplace - the latter is a complex area which requires close observation of the law and employee 'consent' cannot be seen as a silver bullet."
When asked if they think their parents are spying on them, a random group of teens at a busy shopping centre in Los Angeles thought it was highly unlikely.
Parents are too busy, they say. They trust them.
But when I visited a primary school in Los Angeles, where cyber-security expert Lou Rabon was addressing parents at his son's school, many of the parents were open to tracking their kids' every move.
"I would chip them like a dog if I could," one mother said.
Many of the parents there thought they were tech-savvy and were shocked to see how easy it was for Mr Rabon to pinpoint their geographic location by the photos they posted on Facebook - he then taught them how to turn off geo-tagging on their camera phones.
They groaned in horror as he showed online messages a predator had posted in a chat room posing as a depressed and lonely 14-year-old girl looking for friends.
Mr Rabon, who is in the process of creating a parent app of his own, advises parents to use obscure passwords.
One mother told the story of her nine-year-old son who was taught by an older child on the school bus how to get around parental controls on his phone by using a commonly used password in the family.
"Within minutes he had Googled the word 'sex' and my nine-year-old was on a porn site," she told parents at the meeting.
"He saw things we hoped he wouldn't see ever or for at least another 10 years."
It doesn't bode well for parents trying to instil trust and independence in their children.
Mr Rabon says it's naive for parents to blindly trust their kids - and he agrees that in many ways it's a lousy time to be a teenager.
When asked if the next trend would be for teenagers to turn off their phones, he says it wouldn't work - the app he's creating would alert a group of parents if the children in a circle of friends all turned off their phones and would pinpoint their geographic location - ie the party's busted.
"If you want to completely disconnect and raise your children in that world you've got to go to the jungles of the Amazon or something; in the world we live in today this pervasive ubiquitous technology is only going to expand," he says, adding that he doesn't want his sons raised in a bubble, but he can't ignore reality.
"This technology could save lives so I think that it's absolutely a great thing to be able to track our kids."