If you're talking stillwater, yes, you detect strikes mostly by "feel". If you're going to nymph with the line in moving water, you will probably want to use something like this: http://www.fishingwithflies.com/Fly-Lin ... ators.html

You can attach them at different points on the line. Since you wouldn't be able to use a traditional strike indicator setup as with a floating line, those would be your best bet with a sinking line in moving water.