Even though that's just a shocking tool, not a "taser." Why don't you just buy a real gun and learn how to use it if you want self-protection? Tasers should only be used by law enforcement in lieu of lethal force. They have the training and understanding of its use and can therefore make effective use of such a tool.
Civilians using tasers are liable to miss their target because of lack of training due to the cost of those expensive taser cartridges, the limited usable distance of the taser, and poor aiming ability of those tools. Even if a hit is registered, the taser can only incapacitate a single assailant without enduring a lengthy reload and its user will be left with no defense against other assailants.
A hand gun is far more lethal, has greater threat capability, and is much easier to train and become familiar with. Except in situations where you only wish to incapacitate, rather than kill--which only applies to law enforcement--a handgun is always a superior solution.
If you kill, even if it's in clear self defense, you are still likely to go through a world of legal grief.
The point of a took like this is simply intimidation. For the purposes of self defense, I would personally much rather have any number of other tools.
There are also legalities to consider. Unfortunately many of us are stuck in nanny states, where cops think they should be the only ones entitled to carry weapons for the purposes of self defense.