It's a good idea, but three thoughts.
A. Training has to be valuable to the company for the employee in there current role or a role they can easily transition into.
B. More risk should equal greater reward. I could easily punch out an A+, Network+ and Security+, with the same effort required to pass just the CCNA.
C. I think you'll find even with these rewards, few employees would be willing to invest the money to improve themselves. They would be more than Happy to spend the lots of $ to get that new 4k HD curved TV or fancy sports car, but if you ask them to spend a few hundred dollars to learn to swim when they work on a ship with shark infected waters all around, they will look at you with pure horror! How dear you ask me to spend MY own money to make myself a better employee.
paul78 said: I'm not a fan of offering a raise simply because someone has a certification or passes a certification. I've always believed that an employee's performance and value to the company ought to dictate their compensation. If your company provides IT consulting, etc. type services where someone with a specific certification can translate to increased billable rates, then it would make sense. But I would really caution against giving someone a raise for passing a certification. Plus - you have to consider how it would translate to non-IT departments as well. That said - if you want to offer a monetary reward for passing a certification - my suggestion is a one-time bonus/reward instead. And I would personally do something on the smaller side like giving an $100 - $200 gift card. Also - if you keep the reward smaller - you can be more generous with the type of certifications that someone has to pass. It could be broader and maybe even not directly related to the role of the individual.