For those like myself, wondering why is this significant, here’s a comment from Reddit:

Here’s a long answer. To the first question, “What’s the significance of 915Mhz?”

In the United States, all devices which emit electromagnetic energy (radio waves) are legally under the purview of the Federal Communications Commission (FCC). The FCC publishes regulations which state the conditions that must be met to make these emissions legal. Most of the time, the rules primarily relate to the frequency and power of the radio waves being emitted. Secondarily, the intentions of the device owner are considered.

So what’s special about 915 MHz under these rules? 915 MHz is the center frequency of a band of frequencies, stretching from 902 MHz to 928 MHz, which has been set aside for “Industrial, Scientific and Medicine” use (ISM). Subject to several other conditions, this band is free for anyone to use for nearly any legal purpose.

This is unlike other frequencies, such as the band from 88 MHz to 108 MHz, which can only legally be used by commercial FM radio stations, and only then if they’ve received a license for the specific frequency they’ve been assigned and hired licensed engineers who ensure that the signal won’t interfere with any other licensed stations and obeys other technical requirements.

There are other ISM bands beside 902-928 MHz. One of them is at 2.4 GHz, which make look familiar as well.