That's one I'm going to need an answer on next spring -- Eric will start riding lessons and he, unfortunately is too young & wrong gender to wear a bra :) I think for the time being since his lessons will be very short (30 min is all a little guy can take) I'll just take it off, but I wish there were some male riders out there who could tell me how a pump is managed on horseback.
I wear jeans when I ride, and I just put my pump in my front pocket. It has never budged from there. Fits fine, and it doesn't get in the way.
I always ride with my pump in my front pocket. (when im not riding, its in my back pocket). Ive never had any problems with it. I ride western or bareback.
Once something spooked my horse while I was riding bareback. I got thrown off, but my pump never came out of my pocket and remained unscratched. :)
I'm on the OmniPod now, so i dont have to worry about tubing getting caught on a stall door or anything (trust me, i've been there). now when i ride, i just check my sugar before and eat a snack with protein and carbs if needed. depending on how intense my ride will be, i might do a temp basal as well, but i normally dont ride longer than an hour so using a temp basal is rare.
back when i was in college and on the IHSA team, i would do something really dumb. i took my pump off all together for like hours. since we were riding the host school's horses, i was nervous i would fall off and break my pump. i never fell off at a show (but managed to fall a few times from horses i rode consistently at 'home'). i would not suggest 'unplugging' your pump during riding or work time....it's just a bad move.
as for a tip to keep the pump 'safe'... you could just always go for the OmniPod and get rid of probably 90% of your concerns straight away. no tubing and it's always hidden unless you put it on your arm and wear short sleeves or tanks. i know women who wear their pumps in their bras, although i've never done it. i guess it would work better with a sports bra than a normal bra, but it would be a personal preference thing.
back in college (this was when i was on the Deltec Cosmo pump) i also used to wear my pump clipped to my breeches by the small of my back. that way it was out of my way by not being on the front or side of my body to get caught on something. i would be sure to coil the tubing and place it right below the waistline at the hip of the breeches so i could have access to it if needed, but it was still out of the way.