“When my kids were younger, I used to always drive them around and show them all the Christmas tree lights,” Mr. Walters said in a telephone interview. “I just thought it would be nice if there was an app that would do the same thing.”

The app allows users to geotag (mark on a digital map) any place where they find a particularly dazzling display of lights. It is, essentially, a collection of holiday-themed spots available to anyone who downloads the app.

Though the app is glitchy and crash-prone on the iPhone’s newest operating system — Mr. Walters is considering a fix — it is easy enough to use. A simple panel opens with two options. One allows you to view a map of local light shows; the other allows you to add one yourself.

The app has not seen much use in New York City this season. In the suburbs to the north, there are displays emerging in Eastchester and some other areas. Last week, however, the entire borough of Brooklyn had only one location demarcated.