your ecu needs a speed limiter to start with, and from there you need to check the voltage range off the VSS sensor, some honda's are cable driven though, from there you'll probably be making a custom board that will cut throttle if the resistance reaches a certain point. A cruise control unit will probably jump start you on this.
For the most part if you are doing this it's going to be completely custom writing of software and time consuming. It will accomplish less for more than just chipping to begin with. This can cost $5 (if you solder the chip in yourself) up to around $200ish, but it really depends on what vehicle and OBD you are working with.