Hi mark
As you can wear the pump and keeping it out of harms way, isn't too much of a problem, etc manufacturer have several different types of cases, clips and straps that you can use to locate your pump around your body in verious ways... And its not very difficult for a pump user to adapt other items such as mobile phone cases, baby socks etc to fit there needs..
As to catching the pump or it's tubing or having this pulled out, this would mainly depend on the due thought of the officer and how and where he/she might place the pump, if they place it under clothing and it's secured in a good manner this would cut down the likely hood to a very mimium.
I am a dog handler myself, I was dealing with a very large ill-mannered staffie, who was constantly jumping up at me, my pump was cliped to my waist band, the dog managed to catch his back paws in the tubing of my pump, pulling this to the ground, the pump stayed clipped to the waistband and the infusion set also stayed put, however my tubing that is 60cm long ended up about 100cm long!!
It is possible to have infusions sets pull out, as you see this isn't that easy if it does happen it isn't a big cruises, as the cannular part of the infusion set is only very small, and it is unlikley that you would even bleed...
I do know of several pumps users who do ride horses, so for horse riding wouldn't be a problem, most manufacturers do discourage the wearing of pumps durning contact sports, The insulin pump has been taking to all sorts of places round the world, up mountins, through the desert to the artic even Sir Steven Redgrave won his last gold medal with a pump....
Sat here thinking about the problems that a active police office might have wearing a pump two things do come to mind as a general view, most police officers carry communiation kit, which are connected to both there belts and clipped to shoulder straps (things) also they might have other attachements to there belts the pump wouldn't be much different than this type of kit in many ways.
The other thought, a pump and insulin supply is carried with the officer at all times, the officer can adjust the pump to suit present needs situation, which even with well controlled MDI, this isn't always possible so a serving officer is less unlikely to be foiled by his/her pump than the MDI...