I don’t know how many Jewish members we have here, but this is pretty handy. I found it in the Play Store. It’s not perfect, but it is functional.
It uses my map co-ordinates to get the sunset and allows me to set an alarm for any minutes before sunset. It does not allow me to choose the alarm sound.
I am not Jewish, but I keep the sabbath. I don’t go as far as not turning on a light switch and such, but I don’t get out there and mow the yard, or do any labor.