Plenty of options exist when it comes to home security systems. But at least three things are true about most of them: They are expensive, require a contract, and are limited to what they can detect via movement to trip an alarm.

That's why Denver-based startup Notion created its home sensor: a nonintrusive, cookie-size device that can be placed on any surface to detect changes in light, sound, and a variety of other elements. A set of the devices, when combined with a Wi-Fi-connected hub, offers traditional monitoring--movement, broken windows, opened doors--as well as the ability to notice subtler aberrations like temperature changes and water leaks. The system sends all of these alerts directly to your phone.

To be sure, Notion isn't the first to create an internet of things-connected, do-it-yourself home security system. Canary's smart home security system uses a camera and microphone to detect movement and alert the homeowner, and Nest Protect smoke alarms detect smoke and carbon monoxide. But the Notion combines these elements and others into one product that can be installed in each room.

Compared to detecting a break-in, sensing a water leak may not sound like a terribly exciting feature, but Notion includes that capability for a very good reason: Water losses are responsible for $8 billion in paid insurance claims each year, according to risk assessment firm ISO. And even though most insurance policies do cover these accidents, no one wants to endure the weeks or months it takes to dry, gut, and repair a damaged home--not to mention the premium increase that's sure to follow.

Notion's devices are designed to help homeowners realize these leaks are happening before the damage becomes severe. Placing a sensor near some of the most likely sources of water escapes--dishwashers, toilets, tubs, sinks, and water heaters, as well as in flood-prone basements or ground levels--could help make sure a potentially massive spill stays limited to a mop-up.

Brett Jurgens, Notion's co-founder and CEO, says that 85 percent of water leaks come from appliances, whether it's a broken valve or a hose that comes loose. By strategically sticking a sensor on the floor near these appliances, you can cover several bases. The device sends an alert to the owner's phone as soon as it detects liquid--and it's water resistant, so identifying a leak won't result in your sensor's valiant death.

The idea came to co-founder Ryan Margoles several years ago, when the smoke alarm went off in his house while he wasn't home. It turned out to be a false alarm, but Margoles thought about what good the shrill beeping would have done him--and his new, nervous golden retriever puppy--if there had been an actual fire.

He and Jurgens, who have been friends since they were 4 years old, weighed the idea of attempting to design a smart smoke detector for the masses. They ran into a number of challenges, including regulations, and the fact that most people don't buy smoke detectors--they use whatever's already installed when they move in. Instead, the pair switched gears to a smart device that would hear an alarm and then alert someone remotely. That idea quickly grew into a product that could notice many other disturbances throughout the home.

The Notion sensors are small and sleek. "If we're creating a product that you're gonna put in every single room," Jurgens says, "we want it to be a little bit hip--to be additive to your house." But, like many of the appliances they'll be stuck near, Notions are white, so they also blend in.

In deciding on a shape, Jurgens and Margoles thought about the simplicity of installing smoke alarms: No edges means no need to align with walls, floors, or any other lines or angles. "It takes a little bit of the pain out of it," Jurgens says. "Just peel the adhesive off the back and stick it to something."

While home security systems can run around $2,500 for a three-year contract period, the Notion costs $129 for a hub with one sensor, or $269 for five, which Jurgens says is the average for a multibedroom home. Many insurance companies offer discounted rates for homes with security systems, which could mean the device ends up paying for itself. 

The device detects small changes in its environment by way of vibrations. Currently, that's how it notices sounds, like a fire alarm or knocking on a door. A soon-to-be-released update to the software will allow the devices to attach to a container like a gas tank or keg, send out a ping, and then tell you how much propane or beer remains inside based on the frequency of the waves that bounce back.

With further application, this kind of technology could possibly detect aberrations behind a wall, like sudden gushes of water or changes in water pressure. While that particular feature isn't in the works just yet, Jurgens says that as new capabilities are added, they'll be part of a software upgrade instead of requiring new hardware--something that has made companies like Tesla and Apple favorites with consumers.

The company just closed a $3.2 million funding round, bringing it to a total of $5.7 million raised to date from investors including XL Innovate and Liberty Mutual Strategic Ventures. Notion has sold about 10,000 devices through its website and a Kickstarter campaign and says its revenues are around $500,000. Of course, it's still early and there's a lot of competition in the home security device industry, but Jurgens is convinced Notion offers something different. 

"Except for maybe a few, almost all the products out there are very, very single use," Jurgens says. "We're multifunction, where you just need one device and don't have to make any choices. We think we're going down a unique path."