Helmet strap as a lock.
I got a Garmin 530 a few weeks ago. One of the reasons I bought it was for the alarm. I was disappointed with how quiet the alarm is. However my phone will receive the alarm as long I am in bluetooth range.
Most of the time I ride alone and can be selective about where I eat, so here is what I do then.
Chain = Biggie/Smalls.
1 glove around the chain near the RD on the bottom to get hung up when the pedals turn.
1 glove around the chain near the FD on the top also to get hung up when the pedals turn.
Front wheel skewer removed and stuck in my phone mount on the stem so the thief will faceplant the first time the front wheel comes off the ground.
Front skewer locking nut stuck in my pocket so a smart thief can’t put the skewer back in.
Helmet straps wrapped around the seat post and rear wheel and fastened to buy me a few more seconds before he makes off with my bike.
Lastly, I put my bike in an area I can see from the restaurant and I think it would be impossible for anyone to get through all of those before I was on him.
When I am with friends on a casual ride I bring a lock as well.