If you have a cell phone, for a few $$$ a month, you can forward your house calls to the cell phone. Or, whoever is at the house and is leaving to go, say, shopping, they can forward the calls to you and unforward them when you or they return to the house. You can keep the phone on the charger in the shed or hook it up to an AC/CD 'converter' to always be 'hot'.
The only downsides I can think of is you forgetting to unforward the house phone when you hop in the car. If your phone is off, or if it just rings and rings, you 'ring up' these nickle-and-dime charges each time someone tries to call the house/cell-phone whereas you're not there. The only way this wouldn't be a problem is if you have a Phone Plan that has some sort of 'unlimited' this and that, and a 'no charge plan' for this and that. See what I'm saying? My phone only gets a 'break' after 9pm on weekdays, and from 9pm Friday to 7am Monday.
I guess it was worth a shot. My best to ya and hope this helps.