|Boing! Why did the textbox say Boing!?|
First, starting off, the base item is a grapnel. The grapnel can be found in the first Dungeon Fantasy book and in High Tech for $80. Using the rules in Low Tech for Very Fine tools, we turn the grapnel into a Very Fine Grapnel which now costs $1600. This $1600 can go (ST+2)x2 yards, and is thrown by successfully rolling Throwing - 1, adjusting for distance penalties and time spent aiming of course. It can carry... doing some basic arithmetic... 331 pounds.
But the trick is now the climbing part... climbing is not cool because it doesn't capture that instantaneous feeling of a hookshot... Unless we use haste. Haste is a -1 penalty to skill for every 10% faster we travel, up to a maximum of a -10 penalty for a cinematic instantaneous. We can convert that to a technique. The technique is hard by GURPS basic rules because the consequences of failure are dangerous, so it costs a total of 11 points. To this 11 points, we add another point because I will use Metatronic Generators, and we need a perk to substitute Electronics Operation (Metatronic) for a climbing roll. This creates a hand-spun advantage that is worth a total of 12 points.
Now we need to add an accessibility modifier so that the instantaneous climb is only used with the grapnel, and we need to add a gadget limitation for a small metal object roughly equivalent to a weapon, which according to Sorcery is worth about -55%. I use this value instead of the metatronic generator values because it doesn't have the extra special benefits of a metatronic generator. Together we have a gadget based advantage around:
Hook-Shot Insta-Climb (Small Metal Object, SM -6, -55%; Accessibility, Only when climbing the Hook-shot chain, -10%; Nuisance Effect, Chain is kind of noisy, -5%) 
So 3.6 points all together, or 4 rounded up. 4 converts to an additional $1200. Adding that to the original price of $1600, we have a $2800 device. To use the hookshot, one must successfully execute a throw skill row at -1, accounting for range and aim modifiers. On a success, as a free action the user may roll against climb+2. On a success, they are instantly whisked to the location to which the grapnel latched.
Precis - Ramblings of using the metatronic generator rules to build a Zelda inspired hookshot.