Not everyone launching an app needs to be a venture-backed kid out of Y Combinator.

For Gillian Fein, it was simply way to have it all: Spend more time with her two (soon to be three) kids, build something with quick impact, and launch the next phase of her career.

Fein’s iPhone app, LaLa Lunchbox, is a way for parents and kids to work together to plan nutritious lunches. There are some monsters and game dynamics and cool visual effects in there. But really, it’s the outgrowth of a very simple project Fein did with her daughter, Lila, to help plan her lunches.

Fein laminated a peice of paper and cut out some images and labels of Lila’s favorite foods. Every weekend Lila would grab if off the fridge and organize balanced lunches for herself, and then they’d head over to the Farmer’s Market or grocery store and load up on what they needed and then pack healthy lunches for the week together. (That’s the two of them above after Lila’s cooking class.)

It was easy. It was effortless. It was healthy and organic. And her daughter learned where food came from and how to eat balanced meals — even nagging her parents when they didn’t. “We never had an argument in the morning about what she’d have for lunch or any problems,” Fein said.

Nothing about this was particularly innovative from a technical point of view, but friends of hers who were parents saw it and wanted it. A seven-year veteran of New York City’s public health system, Fein was craving something more entrepreneurial and more flexible — two things that don’t always go together. She decided to turn the project into something more interactive and see how many parents — beyond just her friends — would use it.

A lot as it turned out. It launched May 1, and it’s been quite a month for Fein’s small healthy-eating mini-pire. The app has received shoutouts and press from brands like Tina Roth Eisenberg of design blog Swiss-Miss.com and a Twitter shout out from Maria Popova. On May 10, it made Apple’s “New and Noteworthy” section, featured throughout Mother’s Day weekend. That launched it into being a top-ten in Lifestyle category and within the top 250 in the app store overall.

Fein is planning an iPad version and an Android version of the app and more gaming elements for version two.

I played with the app, even though my 9-month-old son Eli still just dines on milk and homemade baby food from the freezer. (That doesn’t take much planning.) The app is very engaging — you can pick monsters to represent different lunch boxes and drag different vegetables, fruits, and proteins into the monster’s mouth to a big chomping sound. That’s all neatly arranged into a shopping list. Given all kids love affair with iPhones, it seems a no brainer way to get them engaged with lunch planning.

The success so far is nice validation for Fein who is now pregnant with her third child. She said people were “shocked” when she made the radical decision to leave work to spend more time with her family. Her boss said to call him when she was “bored” with her kids. “How can you not laugh at that?” she asked. (Indeed, as a new mom I can attest that kids are many things, but boring isn’t one.)

She put a lot of thought into every aspect of the design. Were animals too cutesy? What about monsters? What would appeal to the four- to five-year range without being too “baby” for the eight- to ten-year range? She polled all her children’s friends and friends’ children relentlessly.

Is this the next Zynga? Maybe not. But it also doesn’t have to be. That’s the beauty of technology in this day and age. Platforms like the iPhone and Facebook may be ways to accelerate the path to building a huge business, but they typically require every bit as much money and staff to get there. But they can also facilitate lifestyle businesses for women wanting to spend more time with their kids but have fulfilling careers at the same time.

“Somedays I feel overloaded and somedays I feel on top of the world,” Fein says. “It’s all about finding balance. When it’s time for work, I work my ass off. I’m lucky to have a supportive husband and terrific baby sitters, and I carve out time with each of my kids everyday. It’s important for my kids to see that I’m doing something that matters to me.”