I use a Megaboom 3 these days. I made a simple clamp to hold it between the seats. The iPhone sits in a tray on the rear of the gearbox cover. Tray and clamp were both produced on my 3D printer.

Tim H.
1986 4/4 VVTi Sport, 2002 LR Defender, 1957 R4 CV, 2005 Ferrari Vipar