These devices are intended for professional rope work. When doing rope access work, there are typically two ropes involved. One is the working line which is loaded with the worker's weight. The second rope is a backup line which is only loaded in case the working line fails. An arrester device is running along on the backup rope and moving up and down the backup line with you. If you fall because your main rope fails, it will lock and catch you. As this may easily result in a factor 2 fall on a static rope, a shock absorber is used with such devices. I have used such a setup when doing route-setting and it is really working fine.
However, in mountaineering, the situation is a bit different. For weight reasons, there is typically only a single rope fixed. While mountaineering, one is always moving. When following a fixed rope, there are 3 possibilities:
- Going up: A simple ascender is sufficient, if the fixed rope section is short enough a prusik knot will do just fine as well.
- Traversing: No need for an arrester at all. A locking carabiner clipped into the fixed rope is enough to prevent a bad fall.
- Going down: Rappel the fixed rope. As there is no backup rope, an arrester would not be helpful.
For mountaineering, I cannot really see a use for this.
The only potential use I can see is solo top-rope climbing, for example practicing the crux of your project. In this case, one is typically self belayed by an ascender. If there is the possibility that the rope is running over edges  and might break, a backup line can make sense. The fall-arrester would allow to climb up and down without any hassle and still provide more security. However, the safety standards are a bit different in climbing, mountaineering, and professional rope work. Therefore I have never seen anybody actually use a backup line in this case. Doing a rebelay  is typically sufficient for this case as well.
 Meaning a single rope that one can trust. Old ropes from last year's expedition do neither count as a primary line nor as a backup.
 In case of sharp edges, a rope protector should be used
 This means fixing the rope to an intermediate piece of gear or bolt after the potential sharp edge with minimal slack. The weight is now on this piece and the rope will no longer rub along the edge. This is nicely explained in Dave McLeods video on self belay