Like others wrote, have a notification sent via email and/or text for any charges over a certain limit (I picked $25 for no particular reason). It comes very quickly for us, like minutes, but I have heard from others that YMMV. This is for our Debit/Credit card from a small credit union.

The only drawback is I do get notified for every singe thing that gets purchased (over $25) and if it looks unfamiliar, local or funny at all (like the seller is "XMY DRF" or "19348189289") I ask my wife if she made any purchases. At first she got annoyed, but after a while she figured it out. Just covering our asses.