Grapi Independent of the security reasons mentioned above
I'm sure the OP appreciates the recommendation, but they specifically asked if "is it safe" to use an app. To me this means that security matters for them.
GrapheneOS project member advised:
matchboxbananasynergy please exercise extreme caution
...with apps that have so much control over devices. And for good reasons.
Grapi Regarding Android 4.4, I think you misunderstood the app description in Play Store.
I think they understood it correctly. Please read through the link they provided in their post. This means if security is a concern (and for the OP it is) this app shouldn't be trusted at least till it starts to target Android 14 and up. Let alone the massive control it gets over the device. Google forces this for good reasons. It's safer to use apps that target modern APIs.
With all that said, the built-in functionality that does exactly (or almost exactly) what the OP needs should be the way to go if security is a concern. The built-in functionality for this was left in the OS by GrapheneOS devs, so to me this means they trust it. And if they trust it, we should, too. We all are here because of their exceptional expertise in security and privacy. No need to trust additional custom solutions and raise attack vectors until absolutely necessary (the usual threat model disclaimer goes here).