I have seen a handful of methods and devices on the market: http://www.rockexotica.fr/products/downloads/belay.html (Wayback Snapshot here) These include Rock Exotica's "Soloist", "Solo-Aid", and "Silent Partner" devices.
But its not clear to me that any of the these devices do a better job than a simple ascender would do. Can anyone share any experiences or preferences for solo-top roping gear? (Note: I consider solo lead climbing an entirely different beast and am not asking about that here.)
You should not use a toothed ascender as a fall can sever the rope. Additionally these devices are typically not usable for decent therefore additional equipment is required anyway.
Section 6 of this report has testing of fall-arrest devices:
There is no definitive answer. To quote Petzl "It must be understood that all systems are flawed, because this means there is a risk, however minor." General principles for solo climbing with a fixed belay rope.
The Petzl mini/micro-traxion are what most people seem to use. Outdoor gear lab did a recent comparison with a few other devices.
I've also seen Gri-Gris used for that purpose, though it's obviously not recommended by the manufacturer.
I use a Petzl shunt:
http://www.petzl.com/en/outdoor/multi-purpose-ascenders/shunt
As noted by others, self-belay is always going to carry risks - the shunt has a smooth camming surface so is rope friendly, and hopefully with top-roping you are going to have very limited impact on a fall.
The shunt is used by a number of pro-climbers to help them when they are red-pointing hard sports climbs. Eg. Dave Macleod:
http://davemacleod.blogspot.co.uk/2010/05/in-middle.html
Or at 3m25s on Indian Face (see oddly helpful YouTube comments!):
http://www.youtube.com/watch?v=c3e0AllzcgE
Steve McClure:
http://www.steve-mcclure.com/articlepages/overshadow/
Hope this is helpful!
Rich
