Hi Andy...welcome to the Forum
Firstly, a remap done properly and not too excessive shouldn't present any problems to the engine durability if it is up together, regarding maintenance, belts, etc.
Here's a link to an article on a Tuning Box which is a safe option
http://www.audiownersclub.com/news/reviews/club-reviews/product-reviews/electronic-engine-tuning-guide/
Cheers, Trevor