Built into the Wii Remote is an infrared sensor, that can locate several, punctual infrared light sources and report their location to Remote Buddy.
It's impossible to determine the position of the remote control - and thus also moving the mouse cursor - without at least one of these infrared lightsources.
When using the game console, the so called sensor bar is supplying this IR light source. The name is a bit misleading, as it does not contain any sensors at all, just IR diodes, that emit light in the IR spectrum - which is invisible to the human eye.
If no sensor bar is available to you - or if the IR diodes in it are currently turned off, another infrared light source is required. Infrared radiation is also called heat radiation. Simply said, when there's heat, there's infrared light, too. Using this physical phenomena, you can also use very hot objects as infrared light source - whereas f.ex. tealights and candles are especially predestined. Always make sure to exclude the possibility of a fire and any other risks, when using burning candles, tealights or very hot objects,
An infrared receiver can not be used as infrared lightsource. It can only receive, not emit infrared light.
TV sets and monitors don't create light in the infrared range that would be strong enough, either.
In order to use the infrared mouse mode, you have to point your remote control to the IR lightsource. You can easily check, whether this source is strong enough by having a look at the options of your remote in Remote Buddy's preferences (in the Hardware tab). There, all light sources recognized by the IR sensor are displayed for as long as the IR mouse mode is active.
You can find more information on infrared light on f.ex. Wikipedia (Link to external article).