Nintendo's adding a gyroscope to the Wiimote.

Dynamics
Since all known Wiimotes are in use near the surface of the Earth, there is a constant background force due to gravity, even when the player is not accelerating the remote. (Without the extra knowledge that we are on the Earth, this force would be indistinguishable from player-induced acceleration. A nice reminder of general relativity.) We will assume that all axes of rotation are close enough to the motion sensor that a rotation does not linearly accelerate the sensor. (i.e. there is no lever arm)

The acceleration <math>a(t)</math> measured by the sensor (not the true acceleration of the remote) is then:

<math>a(t) = R(t)(g\hat{z} + a_r(t))</math>
<math>\dot{a}(t) = \dot{R}(t)(g\hat{z} + a_r(t)) + R(t)\dot{a}_r(t)</math>

where <math>R\,\!</math> is the rotation matrix which transforms from the "living room frame" to the local frame of the remote, and <math>a_r\,\!</math> is the actual acceleration of the remote in the "living room frame". The rotation matrix is parameterized by 3 Euler angles, and the remote's linear acceleration has 3 components as well. With 6 dynamical variables, but only 3 observables, our system is underdetermined! However, we can extract some information if we make simplifying assumptions.

Pure Rotation
If we assume the remote experiences no acceleration (most likely at rest in normal usage conditions), then the motion sensor directly tells us which way is "up". From this we can derive two of the Euler angles of the controller, but not the angle of rotation around the z-axis in the living room frame (corresponding to "yaw" in the diagram when the controller is level). This lack of knowledge is one of the reasons it is difficult to control an on-screen pointer with just 3 accelerometers. The most natural motion for a user to indicate pointer movement horizontally is (roughly) to pivot the controller around the z-axis.

However, two angles are sufficient controls for many uses. The "up" vector that the sensor reports can be used directly, or decomposed into angles: <math> Put formula here </math>

I'm not wrong. It has tilt sensors AND accelerometers. Or rather, the latter can sense tilt without movement.

Tilt Position Sensing

* If the remote is not accelerating, the tilt of the remote can be calculated directly using the force of gravity

* If the remote is accelerating, you need to double integrate the acceleration readings to get the change in tilt relative to the last known value.

The main problem with this technique is error accumulation in our estimate of "up." Since it is unlikely the user can keep the controller in constant linear motion without injuring themselves, the TV, or their opponent, we can look for times when the total reported force is close to g = 1.0 to recenter <math>R(t=0)\,\!</math>. You have to be careful when doing this because it is possible and probably common for the Wiimote to report an acceleration close to g = 1.0 while it is accelerating. When this happens your acceleration vector does not actually point "up" and you will recenter to an incorrect R. This can happen anytime you are accelerating both downward and in the horizontal plane.

In your explanation there would be no tilt sensed when the controller is at rest and games like Kororinpa and Monkey ball wouldn't work if you held the controller off-centre a bit (making the acceleromoters central).

it appeared that it was when they showed some people playing one of the star wars games.