Hi All:
The TAIC of NZ report into the crash of an IFR PA31 conducting an ILS approach at Christchurch is significant to this thread, particularly with respect to Safety Recommendation 064/03 regarding the use of cellphones in flight.
Apart from the fact that the pilot appeared to be using his cellphone at a critical phase of flight, TAIC has also concluded that the cellphone signal could also have impaired the GS signal, possibly contributing to the crash.
Go to:
http://www2.taic.org.nz/InvDetail/03-004.aspx
PS: Just noticed dudduddud has also pointed to this incident.