Updated post: Phone *not* stolen from handlebars

I thought I forgot to take my phone off my bike handlebars last night when I locked the bike up to go into a shop, and I thought someone stole it. In fact all they stole was the front half of a £12 light set, which I had superglued to its mount and they ripped off. I just found the phone in my bag, but I wrote the below while thinking it was gone.

I've been mounting the phone on my handlebars for the last four months. I find that satnav makes it much easier to get around in London and avoid using the main roads, but it seems inherently risky because you have to remember to remove the phone after you lock up the bike. I wonder if this has happened to other people and how we reduce the risk. The same issue applies to bike computers (and lights etc), although maybe the risk is slightly lower there because fewer people would recognise an expensive bike computer.

I think it's easier to form a habit of doing something in preparation for doing what you want that it is to remember to do something after - so remembering to remove the phone every time after cycling is somewhat difficult.

There are several things you have to remember to do when locking a bike up in London — in my case I locked the frame and front wheel to the stand, used a cable to connect the back wheel to my d-lock, removed my pannier, and removed both lights. Obviously I should have also removed my phone.

Ideas to reduce the risk:

• Attaching the phone to the riders body with some sort of cable. I'm not sure if it could be made comfortable enough, and it would have to be designed to break easily enough to not affect how you fall if you come off the bike. Easier perhaps if you're wearing belt loops or a belt, or it could link to a wrist.
• A phone app that would detect stillness using the accelerometer and sound an alarm. A bike is never quite still unless the rider has got off, and if the alarm goes off after say 20 seconds of stillness the rider should still be close enough to pick it up. It could be built in to a navigation app and activated when you start following a route. Or perhaps it could be activated by an nfc tag attached to the bike. Not sure how it would affect battery life.
• Something like Kensington Proximo, which can sound an alarm when you carry your keyfob away from your phone. You'd have to have bluetooth switched on on the phone which again might affect battery life, and one reviewer said they had too many false alarms and they had to switch the alarm function off.
• Making a practice of removing all accesseries from the bike before locking the bike. It's probably hard to forget to lock the bike entirely, and by having this practice going to lock it would remind you to take the acessories.

Any other ideas? Have other people lost expensive devices this way?