I've been here a while, and I've never seen this idea posted, so thought I'd write it up in case anybody could use it. I've used it a bit in the past, and it works fairly well.
Here's what you need:
-One of your "extra" ice poles
-One rod holder (or pail)
-One paper clip
-One small, round, plastic bobber (about nickel size works well)
-One short length of brightly colored ribbon
Step 1 - Thread the paper clip onto the end eyelet of the extra rod.
Step 2 - Clip the ribbon onto one end of the bobber.
Step 3 - Set your depth on the extra rod at the point that it will be when set in a rod holder or across the top of a pail.
Step 4 - Pull about 6" of additional line and clip the other end of the bobber onto this point of the line.
Step 5 - Insert the ribbon into the paper clip on the end of the rod. You can adjust tension by inserting the ribbon farther into the clip or by bending the clip. Play with it a little until you get the tension you want.
This set-up works similar to a tip-down. When a fish pulls, the ribbon pulls loose from the paper clip and drops down. At the same time it signals a bight and gives the biter a little slack line. It doesn't work great, but it doesn't work bad either, and it costs about a buck if you've already got the extra rod and rod holder like most of us do. The three big disadvantages of this rig are that it's prone to minnow and wind trips, and you need to maintain the holes to prevent freeze-up. The longer ribbon you use, the more prone it is to wind trips. But, the longer ribbon is more visible, and with a bit of wind will do some jigging for you.
Hope that's usefull to somebody.
kero