Hello guest! Are you an Apistogramma enthusiast? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's a great place for Apisto enthusiasts to meet online. Once you join you'll be able to post messages, upload pictures of your fish and tanks and have a great time with other Apisto enthusiasts. Sign up today!
I can't speak for others, but I've done it. Just make sure you use smaller species. I've used both common types of ghost knives (keep in mind that the blacks especially get large, so won't work long-term) and several other smaller specimens of other knives I've had come in. I used to get in Steatogys (spelling?) species that stayed small, about 6". Just look for small South American species.
The ones I've worked with didn't. All of the small electric knives like this have eaten out of my hands, but not necessarily come up to the surface to do so. So yes, they will eat out of your hand, probably...as for actually coming to the surface, I'm not so sure.
EDIT: re-reading your question, I see you didn't actually say come up to the surface. Even so, whether or not they will come up to you is up to them...but if you go to them, they normally won't run once they get used to the bloodworms. Most are content to eat out of your hand.