If I made a commercial product that utilized radio waves, which frequencies could I use?
The most likely candidates are the ISM bands. Even WiFi and BlueTooth (and many other popular schemes) use the ISM bands. Particularly the 915 MHz, 2.45 GHz, and 5.8 GHz bands.  Note that if you want to sell products, you must have type-approval from the government agencies of the countries where you want to do business even if you use "unlicensed" bands like the ISM bands.

Ref: https://en.wikipedia.org/wiki/ISM_band