I haven't done a studio for awhile - always left a mini plug ended cord for the instructor to plug their iGadget into for exercise music. Nowadays do you provide an airplay device, or stick with a cord for reliability? No wifi in this location, BTW.

You can add wifi yourself. You just won't have internet. IMO the cable is probably the best way to make sure all devices can be connected. From a portable Sony tape deck to an android tablet.

I agree that a cable is by far the more reliable and flexible way to go. We have added Airplay as a "bonus", but always with strong caveats that it's not for "mission critical" use.

I've also done docks before along with bluetooth receivers. With the dock you always gamble on what type of player they have. With the bluetooth they have to know how to link too it, which would seem easy enough.

Even with that the standard headphone cable was ALWAYS included and always the backup or sometimes primary way to work it. Its fast, simple and you can leave enought slack where they can move the player around.