Hi. I'm wondering if an external device may meet your customer's needs.
We've often found a need to keep certain equipment (e.g., mobile routers, laptops, GPS units, etc) powered up for a pre-set amount of time after the vehicle is shut off. Example: A police officer or utility worker turns off his vehicle and is away from it for, say 30-45 minutes. The module keeps the equipment powered up. However, at the end of the shift, if he does not power it down it will be done automatically to save the battery. The module monitors battery V and "knows" the difference between discharge V and charge V. Essentially, the timer starts when the transition from charge to discharge occurs and resets it when the V increases to, say 13-14VDC indicating the engine is on.
We've used a variety of these devices over the years. Examples:
So, with such as device as I've described ignition sense on the router is not needed. Am I on the right track?