The LVD above is okay for a low amp single circuit.
For a starter circuit, or the entire boat you can expect to spend more.
Here's a link to a series of LVD's that will protect starter circuits/batteries and the entire boat (200amp for example).
Battery-Related Products | Low Voltage Disconnect Switches48510 | Cole Hersee - Littelfuse
The cost a bit more than a tenner. They protect more than a single switch on the panel being forgotten.
The advantage is you'll never wake up in the morning and not have the juice to crank the engine, or drive 2 hours to your boat for a beautiful day of sailing and then spend two hours charging a dead lump of plastic lead and acid.
Here's one with a price listed - 130 amp capable, 263 bucks