Replicators first, please.

That’s what I’ve used them for as well =D

Happy planning / planting!

You can check out the toolkit over at Permapeople.org, though I’m unsure exactly how open the codebase is. I do know they’re hoping to make it community run in the future, and that the devs share pretty much whatever is asked of them.

Less in the spirit of your question, but something I’ve used relatively extensively is the mymaps.google tool. Here’s hoping someone with some better answers than me comes along (and I remember to check back) to give additional alternatives