The hurdle with a program like this is the accuracy, that is, the program is only as good as the database of repeaters it pulls from. For many years I was a volunteer coordinator for the Michigan Repeater Council. I can tell you from first-hand experience that many repeaters in the database are "paper" repeaters, that is, they only exist on paper and are not on the air. Another issue is repeater owners can change between DMR, analog, Fusion, and DStar. What is listed seldom matches the repeater's current mode. It is up to the repeater owners to notify their coordination group of any changes, and they rarely do that.
Repeaters are not used like they were at one time. I'm in SE Michigan and several high-profile repeaters sit quite all day. For example, the GM radio club has two repeaters (analog) atop the Detroit RenCen with incredible coverage yet they sit quietly. Another is the KE8HR repeater (Fusion) with an antenna seated near the top of a TV tower. Its coverage is amazing yet for the most part sits quiet. A few other repeaters in my area have some activity but are typically limited to the morning and evening drive cycle. Depending on your location, your experience with listed repeaters may vary.
A couple of years ago there was a fistfight with the ARRL and state coordination groups regarding access to the state's amateur repeater databases. Before the fight, the ARRL would pay each state's coordination council a fee for their state's repeater database for listing in the ARRL Repeater Directory. Since that happened, there has been no accurate all state database of amateur repeaters to my knowledge. Be cautious of repeaterbook, they are not sanctioned by most state coordination bodies. The best method is to poll each state's repeater council for what they have but that doesn't mean accuracy. They can only provide what repeater owners report. You can find Michigan's repeater database
here.
Use the database with the knowledge that if you don't hear a repeater that is reported, it may be a "paper" repeater or using a different modulation method.