Don't just go for the ScanGaugeII, there's the equally good
ScanGauge 'E' which is mch cheaper.
However, as JJ says...if you have an iPhone then get the App
'DashCommand'... but if you have an android, get the App 'Torque'
(the 'lite' version of which is free). As you already use Bluetooth
I'd suggest that you would then require an OBDII WiFi adapter to
connect to either of the Apps, then it's job done and no wires.
I had a Scangauge II, used it a couple of times then shelved it
as I didnt use it all the time, then I got the Torque App, and I tend
to use that more. (I eventually sold the ScanGaugeII).