Train run by doorbell?

I'd just wire it to the doorbell.

I needed a remote doorbell that rings when my front door is rung. I just put a little Chinese transmitter in the doorbell and a relay receiver that rings chimes in my shop when someone is at the door. Obviously, once I get a relay closure, I can automate pretty much anything from there.

$10 in eBay parts didn't sound expensive to me, where is the expense? You don't need to install home automation to do a simple task like this.