Life360 is a startup with a family-and-friends location service that's on an upward path: the company boasts more than 33 million registered families, and it just acquired $50 million in new financing.

In the tech world, growing a company to a certain level inevitably attracts the attention of patent-holders of various types. So it's no surprise that CEO Chris Hulls was confronted with an "invitation" to discuss licensing a patent last week—in fact, he says it's either the fourth or fifth patent demand his company has faced.

But instead of paying up, Hulls found a special way to tell the patent-holders to take a hike:

Dear Piece of Shit, We are currently in the process of retaining counsel and investigating this matter. As a result, we will not be able to meet your Friday deadline. After reviewing this matter with our counsel, we will provide a prompt response. I will pray tonight that karma is real, and that you are its worthy recipient, Chris

Hulls said that he was feeling "a bit aggressive" after getting the new funding and ignored his lawyers' advice "and sent them a snarky response." The patent-holder, Advanced Ground Information Systems (AGIS), sued on Friday—and it included Hulls' "Piece of Shit" note in the complaint.

Life360 offers a service called "Circles" that allows family and friends to see each other on a map and send group messages. It's a service that answers the age-old question of "where are your friends and family, and what are they up to?" As such, it's one more idea that's actually ancient, and in Hulls' view, it has no place being patented.

"We're getting sued for having markers on a map showing where people are and allowing communication between them," he told VentureBeat. "I could show them a Star Trek episode from the 1960s" that was similar.

While Hulls has not hesitated to call AGIS a "troll," a term usually reserved for a company with patents but no products at all, AGIS does offer a product called LifeRing, geared toward military and first responders who want to use handheld devices to keep track of each other's location. Inventor Malcolm K. "Cap" Beyer, a former Marine, founded AGIS shortly after the September 11 terror attacks, according to the complaint:

[H]e realized that many first-responder and civilian lives were lost that day, in part, because of poor communications systems. He envisioned and developed a new system that would use PDAs and cell phones to give users situational awareness superior to that provided by conventional military and first-responder radio systems.

AGIS is asserting four patents, Nos. 7,031,728, 7,764,954, 8,126,441 and 7,672,681. The newest patent, issued in 2012, describes a "method of establishing a cell phone network of participants with a common interest." According to the AGIS complaint, the patents are infringed by Life360's smartphone apps, which include things like software "that allows a user to touch a family member's symbol on a map and initiate a rapid voice communication or text message."

Even for a company that just got $50 million in new cash, taunting a patent troll is a brave move. The math of patent claims overwhelmingly favors a fast settlement. Halls' last troll claim settled for $10,000, which is less than it would cost to hire a lawyer to file even the initial paperwork on a patent case. Taking a case through trial costs $2 million to $4 million for a high-stakes case, and even a win on summary judgment usually involves legal costs in the high six figures. That's on top of possible damages if the patent-holder wins.

Not to mention, there's been "scuttlebutt that they're likely to be acquired" in the next 12-18 months, according to PandoDaily, which first reported on Hulls' note and the lawsuit that followed. Active and expensive litigation doesn't look good to potential acquirers.

Hulls says he still feels good about his decision.

"My plan is to take this fight for the duration, invalidate the patent, and make sure they can’t do this to anyone else," he told Pando. "We are right in the sweet spot where I can still make these brash decisions and apologize for the mess later.”