The big problem I have with the autograpnel is that according to the entry, when it hits a target, the wielder gets a free Pull Combat Maneuver Check with a bonus of +16. Pull is a monster special ability that is supposed to have distance pulled upon a successful CMB check listed in its entry on the creature stat-block. There is no distance listed for the autograpnel. I assume it isn't "as far as the PCs want," because it takes a full round action to reel in an object weighing no more than 100 lbs for 20 feet of distance. I also assume this because it would be gross and overpowered to pull someone right to you from across the battlefield in addition to dealing 1d6+6 damage and bypassing DR & Hardness as an adamantine weapon.
Also, what kind of an action is it for the wielder to detach the grapnel from a creature, and is there any way for a victim to extract it other than snapping or destroying the cord?
The full stats are in the Technology Guide.
Grappling Hook! - Mabel Pines, Gravity Falls.
Yay! Gotta love Autograpnel!
Range: it has a maximum range of 300 feet, but 30 feet before accuracy becomes an issue.
As far as extraction, ouch! There are no rules in it's stat block, but it's going to hurt no matter who does it, I'd probably say a move or standard action causing the amount of damage from getting hit, or at least the minimum damage, if it's the person who got shot is trying to extract it I'd probably require a combat maneuver check if they're getting pulled by it.
Have fun!