Rooibos seedlings. Or at least, they're supposed to be rooibos. Ebay, you know how it is- though at least the seller is based in South Africa, and sent me free seeds along with growing guides for the plants. A step in the right direction as far as ebay sellers go. Will be curious to see if they grow or not. I'm basically shooting blind here because they are notoriously difficult to cultivate outside of their native environment, so there isn't much information on them.
I accidentally overwatered them this last time so hopefully they pull through... this is one of the only photos of a seedling I've encountered. I don't think overwatering is ever a concern in its native environment.
I was thinking a particularly nasty cactus might better serve.... It might not prevent your garden from being watered by drunks in the night, but it will prevent it from being watered by the same drunk twice.