[Android Apps and Games] kevin@TeslaCoil:
JeepFreak PM'ed me asking for some input so I'll provide it both as a dev and as a user.

Lock screens are tricky to implement. Android doesn't officially support replacement lock screens and I'll admit to a fair amount of API abuse in order to get WidgetLocker to work as well as it does. But I've thus far avoided implementing any custom security for a few reasons:

1) Making it actually secure. Android's built in security is not perfect, but it is secure. Third party apps can't fully deactivate it once it's locked. The APIs that let you bypass part of it only allow that part. (This is stock Android, I know manufactures addons introduce security flaws). A third party app simply doesn't have the same information or abilities as part of the rom.

2) Reboots are hard. Android sends a BOOT_COMPLETED signal to apps (if they want it) however it's near the end of the boot process, meaning the stock lock screen is already active and the Launcher is active behind it. One way around this is to act as a replacement Launcher (Like WidgetLocker's HomeHelper) however this can cause the actual launcher to reload sometimes as it's removed from memory.

3) Explaining things is hard. If adding a kind of fake-security, that's just meant to deter a friend (or cop I guess) from messing with your phone, then some users won't realize it's just meant as a kind of fake-security and will freak out when they realize it can be bypassed by such and such method.

One not-well-known option, if you're on GSM, is that if you pull the SIM card, all your accounts credentials are revoked, locking out gmail/etc. I haven't tested if deactivating the sim remotely (via a phone call to the carrier, or maybe from some carrier's websites) would trigger the same thing but I imagine it would.

It can be very confusing if the phone is actually on or not, especially since there is a slight lag between when you hit the power button and when the screen comes on. On AMOLED screens it looks like the screen is off, on LCD screens the backlight comes on, but could be set to be pretty dim (Setting backlight all the way down may cause the screen to actually turn off and ignore touches)

This could actually be done with WidgetLocker by setting the background to black, then using the back button to unlock. After I release the update with themes you could even have an invisible (or all black) slider so you slide to unlock but only in a certain position.

Not that using a calculator while driving is a good idea either...

If I end up adding security to WidgetLocker I'll make it themable as well so it would be possible for the pin screen to look like a calculator.

I assume you mean this for a lock screen that wouldn't normally be activate automatically. See above about reboots.

The best setup would be for the sdcard to always be encrypted (And still usable as it'd be mounted via loop back ( https://help.ubuntu.com/community/EncryptedFilesystems ) so it's still usable normally by other programs. Then even if the enemy pulls the sd card right away it's not usable. This kind of encryption must be implemented at the system/rom level.

Getting bug reports for such an app would be tricky to deceiver :).

This would also be possible with WidgetLocker using a custom background that looked like a crash screen. There's no current way for tapping the text a few times to unlock, however a third party dev could implement a widget or shortcut that did such a thing.