Within the Blue Proximity

Overview

I read about the awesome little program called Blue Proximity. It’s a Python script that repeatedly measures the signal strength from a selected Bluetooth device. It then uses this knowledge to lock your computer if you are further away from it, and unlock it or keep it unlocked when you are close to it.

It’s very simple to setup. It has a little GUI from which you select which device you want to use for this and then specify the distance value at which to lock/unlock your computer, as well as which time delay for the lock/unlock process. The distance can’t be measured in meters/feet, but instead just a generic unit. This unit is an 8bit signed scale based on the signal strength measured from the device and isn’t terribly accurate. It’s not a perfect science and a lot of factors affect the reading.

So the general idea is that you try and get your environment as normal as you would usually have it and try different values for lock/unlock distances until you get a configuration that works best for you. There are a few more advanced parameters to play with as well. Especially the very useful ring buffer size, which allows you to effectively average that value over the last few readings, instead of using the raw value each time. It’s certainly worth playing around with these values until you find what gives you the best result.

You can even go as far as specifying the commands to be executed for locking/unlocking the screen. The default is probably sufficient for most purposes, but it’s definitely available for those that want to run other commands.

Beyond just locking/unlocking there is also a proximity command feature, which will ensure that the computer doesn’t lock from inactivity as long as you’re close to it. This is very useful for times where you’re watching a movie or presentation and don’t want the screen to keep locking just because you didn’t move the mouse or type on the keyboard.

My Setup

Before I had this program I would have my computer lock after a 10 minute idle period. Then if I return it would almost be automatic for me to start typing my password. The Gnome lock screen is optimized cleverly, in that you can simply start typing your password even if the password dialog doesn’t display yet. It will recognize the first key press in a locked state as an indication of your intent to unlock the screen as well as use it for the first character of your password.

After I configured and hacked Blue Proximity to my liking the screen would lock as soon as I’m about 3 meters away from the computer, and unlock when I’m right in front of it. I configured a 10 second ring buffer to average the reading it gives over the readings for the past 10 seconds. I also made 0 or higher values (closest reading to the computer) count as double entries. Meaning when 0 values are being read it will average down to 0 twice as fast. This allows for it to be more stable when moving around, but unlock very quickly when standing right next to the machine. It all works very well.

It’s been a few days now, and still when I get to the computer and it unlocks by itself I’m amused. Sometimes I even start getting ready to enter my unlock password when the screen is automatically unlocked. Very amusing.

It’s not perfect, and sometimes the screen would lock while I’m busy using the computer and then immediately unlock again. This is to be expected from the nature of wireless technologies, though I’m sure a bit more hacking and tuning will get it at least as close to perfect as it can be.

Conclusion

It’s typical of the software world to always produce amusing and fun utilities like this one. This one is definitely one of my favorites.

So Why Love Linux? Because there are tons of free and open source programs and utilities of all kinds.