Q: Are there any patents for online databases for gravesites/cemeteries?

A: I'm not aware of any such patent and a cursory search of the available databases don't turn up any such patents. (though there was an interesting one which incorporated video into a gravestone!) However, this doesn't tell us if one exists either in the US or in other jurisdictions. To answer this question, you would either need a patentability search or a freedom to operate analysis.

In a patentability search, a patent attorney would search through a number of sources to determine if there are any applications which would relate to your invention. Normally, a patentability search would cover all available information related to the invention, but since you just asked for patents, it could be restricted to only patents granted in this or another jurisdiction.

Alternatively, if you did not plan to file an application but just wanted to know whether you could make a product without infringing on a patent, you would want a freedom to operate analysis. The freedom to operate analysis would review the available applications and patents to determine if you can make a product or perform a specific method without infringing on a patent grant. First, I'd suggest doing a search for yourself. If you come up with something that is EXACTLY your idea, you can determine for yourself if it's a waste of time to continue. If you want to move forward after doing your own search, it's advisable to seek help from a licensed patent attorney.