Chinese version comes is limited to 20km/h while International version is limited to 25 km/h. These limits can be increased by replacing the MC firmware. Depending which firmware version you install, you will get different speed limits:
There are basically two options:
Both applications works in Android only and require bluetooth. Modifying the speed limits with this applications is very easy and does not require any special skill.
If you goal is to remove the speed limits, probably QiHack will work better for you. QiHack gives more control by allowing the user to define speed limits and assistance level, that is, power send to the electrical motor in proportion to the power developed by the cyclist in the pedals. These two parameters can be configured for each riding mode (Full, Normal or Eco). The QiCycle unofficial application, however, does not allow to change these parameters. The firmwares that are installed have a predefined configuration and cannot be changed. In the other hand, the application is also useful for tracking your daily use of the QiCycle.
As far as I know, no bike was damaged by changing the firmware. However, you should be aware that running the motor out of its specifications can decrease the life of the electrical components. For example, using QiHack to bypass the "5-seconds acceleration shutdown" while running the motor at maximum power could overheat it and damage it.
Please keep in mind that changing the firmware could void your warranty.
At the moment, nothing easy is possible. Flashing the MC with a external programmer or rewiring and connect it to a different controller with bluetooth module are the only possibilities.
Different persons are working on developing a solution for bikes without bluetooth. This section will be updated in the future to cover any progress.