A UIQ 2.1 SDK based upon Symbian C++ is freely available from the Sony Ericsson developer website.

Because of this openness, many third-party applications exist that can be used on the P900 and other UIQ phones (such as the Motorola A1000 and BenQ P30).

It features a small QWERTY keyboard and enhanced software, as well as double the P900's memory (64 MB, versus the P900's 32 MB) and supports Memory Stick Pro Duo, allowing the phone up to 4 GB of storage on a single card.

[4] The P900 is the first Sony Ericsson product for which Research in Motion's BlackBerry wireless email service will be available.

This is usually done for four reasons: Though this may seem all beneficial, there may be the drawback of not being able to connect to certain Bluetooth headsets (however, this is rare).