Brainstorm

Leave a Message somewhere on the device what the user have done while the device was locked. (something like the Messages you get when you have new EMails or a SMS)

This Solution could help at alearts from the calendar, but it wouldn't help when you answered accidentally a call of your mother in law. ;-)

This solution points only at incomming calls.

When a call is comming in there should be a button to silent a call fast.

Under this Button there should be a Knob to wipe. Wipe it to the left to cancel a call and wipe it to the right to answer a call.

Some users of n900 have a problem pressing Reject button instead of Answer. Especially when they operate by one hand or in gloves.

In landscape mode everithing is ok, both buttons are split vertically.

In portrait mode those buttons are split horizontally so many people accidentally press Reject button.

A fast workaround could be to enlarge the space between the two Buttons or change the size of the Area to press. 2 examples are added.

Advantageously this wouldn't help when you press it by accident in your pocket.

Thanks to Zeed for the Idea and the mockup.

Edit: Added a additional picture by Zeed with swapped buttons.

When phone is locked (keybord and screen) and an event (phonecall, message,

alam or whatever) happends, the screen could show the original swipe (like if you press on/off button)

and after swipe show event (or phonescreen for answering calls)

Add an option in the settings, called "Allow applications to unlock screen", ideally with a list of applications, like phone, calendar, etc, and "other".

User should have a choice to allow unlocking or disallow it, in which case the unlock screen and swipe stays on.

Idea from onutz:

The call / alarm event should trigger both the main gui (i.e. the calling interface) and a parallel / consecutive secondary event.
This secondary event is just a superposing of a mask (a simple picture) that contains either a slider or two distinct buttons, say 1 and 2; in order to get an action, first you will have to move the slider on the mask or to push the buttons in order: first 1 then 2. This action would be required only to clear off the mask, not to answer the call / stop the alarm. After clearing off the screen, you can answer the call / stop the alarm.

The issue I see here is making the mask available for both portrait and landscape, then to make the mask semi transparent in order for the event behind it (be it an incoming call or an alarm) to still be visible.
 

See the additional mockup. "the mask is a distinct event" - "this is a (unappealing) workaround"

Here are the Posts from onutz: #12, #14

One solution that doesn't require any UI changes could be this:

When the event happens, check the proximity sensor:

a) if the proximity sensor stays uncovered for 200ms, unlock the screen.

b) else, do not unlock the screen and continue to monitor the sensor. When the sensor becomes free and stays uncovered for at least 1 second (maybe 2?), unlock the phone. Of course, one can always manually unlock the phone before waiting that time.

All the times suggested here should be fine-tuned, of course.

Although swiping prevents accidental button presses, and is useful to many, some might view it as an unnecessary inconvenience.

Add a toggle to this feature:

Settings > Phone > (Under new heading 'Interface') > Pressing button 'Actions' yields two options > Swipe to activate OR Button only

This could be useful to those who do not have a problem with the phone interface, and those who are just used to what it is already.

Why not implement someting easy like dubble tap? This would lower the chance for missclick and is just as easy. Single tap to open the screen and dual tap to start the function. Or the other way around.