The cheapest that can read and clear SES light is the $20 MaxiScan MS300. Depend on the state, you can have the code read (and maybe clear) at your local auto part store, too.
The most comprehensive one for use on your X5 is the INPA system. You can built one for relatively cheap.

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00 E39 DINAN S1 //M5 (82k miles)
06 E53 DINAN 4.8iS, born 2/18/2006 (126k miles) http://www.xoutpost.com/bmw-sav-foru...s-my-dslr.html
90 Straman Z32 TwinTurbo Convertible, (1 of 44 ever made) 5 speed, 444rwhp/451rwtq
01 360 Novitec Spider F1 (26k miles)