Android and iOS have a concept of a \"density independent pixel\" so your layouts look the same on devices with different densities and screen sizes.
Up until now I\
Points are density independent pixels (to a good degree of accuracy).
For BlackBerry, the most relevant class is net.rim.device.api.ui.Ui
which defines a UNITS_pt constant (and a UNITS_px constant), a convertSize
method to convert between points and pixels (since operations on Graphics
take pixels instead of points).
A useful methodology for BlackBerry apps is to take everything in relation to your font sizes, which you define in points - there's a version of net.rim.device.api.ui.Font.derive
that takes a units parameter and makes it easy to get fonts with a particular point size.
Of course, you can't take anything for granted - defining things in points will make things easier, but with BlackBerry you deal with lots of different pixel densities and aspect ratios so test thoroughly, at least on the simulators.