To answer your question:
Chronomite Laboratories, Inc. makes several sizes of Tankless Electric Water Heaters called “Instant Flow”. You can choose which is right for you by determining GPM and desired temperature rise at that flow. For product info call 1-800-447-4962(outside CA) or 1-800-447-4963 (for CA residence). I wouldn’t recommend using on every hot water fixture, but for one or two “point of use” applications, this is probably what you are looking for.