Not really an issue with today's designs and better manufacturers. I've been carrying the PPQ, which is fully cocked, for 3 years now from morning to bedtime. The thing gets knocked on nearly everyday between camping, cycling, motorcycle crashes, rolling and flipping around on the ground playing with my son, crawling in and under the cars or truck in the garage, etc. As said above, as long at the trigger is fully concealed and protected inside a holster there is virtually no chance of an AD. They all have built in safeties to prevent mishaps.
That P99C is a great choice if you want the decocker or just go with a PPQ or the smaller PPS. All spectacular firearms that don't get the recognition they deserve.