I only know about Cahulaks because of Polisurgist's answer.
Cahulaks from Dark Sun are essentially two grappling hooks connected by a rope. From the Dark Sun Campaign Guide:
Cahulaks: This double weapon features two four-bladed, hafted heads separated by a length of rope. The secondary end is light enough to be used as an off-hand weapon. When one end of this weapon is held by the haft, the rope is long enough to grant the other end reach. The entire weapon can be thrown.
If you start with this and make a few changes, you should have what you're looking for.
Cahulaks address most of your mechanical criteria. Feats will need to be taken for some of these.
Should probably be reach
Cahulaks have reach.
Should be able to pull opponents
The feat Cahulaks Expert lets you swap a level 6 utility power for a power called Drag Behind that lets you drag immobilized or prone creatures.
Should be able to bind opponents (slow effects or restrained or something similar)
The feat Cahulaks Novice lets you swap a 3rd level encounter power for the Tripping Cahulaks power, which can both pull an enemy and knock them prone.
The feat Cahulaks Specialist lets you swap a level 9 daily power for the power Binding Cahulaks, which knocks a target prone and immobilizes them.
Should still be able to be used as a standard grappling hook
This is not the case. You would need to create house rules for this. This could be as simple as adding the property "may be used as a grappling hook". Grappling hooks already exist as adventuring gear, and are usually obtained via a climbing kit.
It could also be more complicated.
You would need to decide whether the rope attached to the hook as part of the weapon is sufficient, or if the rope would need to be replaced with a longer one. If it needs replaced, you'll have to decide how long that takes, and so on.
Should be easily placed into the existing framework of magical weapons
Since cahulaks are an official weapon, there are enchanted versions. They are in the Flail group.
I might drop the off-hand portion of the weapon so it's no longer a double weapon, but instead simply two-handed. The off-hand would hold the extra rope slack. This allows for a longer rope, which lets you use it as a normal grappling hook.
You might consider increasing the reach to reach 2, but I'd be careful about that. The cahulaks is also a heavy thrown weapon. Perhaps if you dropped the ability to be thrown that might balance out longer reach.