The "fahgettaboudit" chain and others like it are six sided, hardened steel, security chains that can't be cut through by bolt cutters and would be difficult to cut with a grinder. A quick internet search finds only 4 sided chains available in bulk, which could suffice, but are actually more expensive than the 6 sided. I haven't seen the 6 sided available for purchase separately. I like the idea of using old tubes as the frame protector, but these come with a fabric one that works well. Only downside is they weigh a lot.
A round link chain from the hardware store is about as worthless as using a cable with a master lock. Bolt cutters will snap it right off.