Having to duck down and touch the ground seems like it's a bad idea to do when things are hectic, which seems to be the kind of place you want to do something like this.
Instead, if you want to go with the idea of the ring, how about a ring that has several small gemstones placed in it, and you can take them out and throw to where they are supposed to place their effect. So when you're running, you can keep running and just throw down one of the stones instead of stopping, crouching down, casting, getting up again, continue running.
Depending on how you implement it, you could also make this a potion, saying that there is only a finite number of gemstones on the ring. The benefit to this would be that you can give the ring to others to use as well. But the gem you throw could very well just be a conjuration that allows you to aim the spell to where you want it to go, so you can use it as often as you need (with the "spend a mental stress to use again" rule).
