Any suggestions on covering an outbuilding located 150 feet behind my home, just out of reliable range of the base station

Hi, We have loved our Simplisafe system now for two years but need to come up with coverage on an outbuilding behind our home. We tried various sensors but the Simplisafe base station would lose connection to them intermittently. Is anyone aware of a solution that does not require us to buy a complete system for just the building?  We live in a rural area where hundreds of homes have out buildings so I think some sort of extended range or a device we could connect up to our system using the internet connection that we have inside the outbuilding. Really want to stay with Simplsafe but we need to cover the building without two separate systems.