Chris, the airbag moto jackets have a lanyard feature, but it's a really stiff one to prevent accidental deployment when you forget to un-clip before getting off the bike. That would not be possible for the Spot, due to it's size and the nature of it's construction and mounting.
Don't over think it. 99.9% of the time, you're going to want to see the spot and be able to access it's buttons easily so you can send a Ok or Custom ping and see that the unit went into that mode. You have to press and hold the button for 3-4 seconds, so it's not something done by feel alone.
On the Spot 2, you don't have to exit tracking to send Ok and Custom pings, just press the appropriate button, it pings that for 20 minutes, then returns to tracking automatically. On the Spot 1 you had to turn the tracking on again after sending an Ok ping.
Now if you never use the Ok or Custom buttons, it may not be an issue to have it in a pocket or to use the arm band. I use the Ok when I'm stopped for more than 20 minutes and the Custom to let peeps know I arrived at my destination before shutting the Spot off.