We offer the Elderid Ohm for use by climbers that are mismatched in weight. It is a cam-type device embedded in a quickdraw that is clipped to the first bolt. We rent them for day use or sell them at retail.
It works really well when used correctly and opens up climbing partnerships that are not possible without it.
A few things about the OHM:
1. It should only be used by climbers that are more than 1.4 times weight difference. Using it with climbers who are close in weight will lead to very hard catches and an increased chance of injury. So a 90lb belayer can use it with a climber that is at least 126lbs. A 125lb belayer could use it with a climber 175lbs or more.
2. Look at the Elderid site (http://www.edelrid.de/en/ohm/) and watch the video on use before you try it and ask our staff about its use.