I've been looking into this for some time now, and I've currently decided against Bluetooth.
The big problem is that currently, Bluetooth audio is still dependent on too many other factors (mounting location/device compatibility/Bluetooth version, etc). The little bit of info I could find on this amp, I couldn't even find what version of Bluetooth it's running. It seems to have trouble handshaking too. There's still a lot of accessory devices running on v3, which I'm pretty sure has a pretty limited audio quality (like bad youtube vid). Plus, there's another issue. You're gonna burn through battery transmitting Bluetooth, so you're gonna need to charge, so your device (phone, tablet, whatever) is gonna need to be plugged in.
With that in mind, USB OTG is the way I'll likely go.
USB DAC, using USB on the go, which is supported by most modern phones/tablet.
http://hifimediy.com/DACs/android-dac
Hook that and the phone/tablet up to a usb otg compatible splitter- plug one end into a USB charger, another into the DAC and the final into the phone.
Then hook the DAC into a headphone to RCA adapter and plug THAT into an amp.
BAM- You now have near-audiophile quality signal for around 50 bucks USD using any amplifier.
Need it to be even better? Use this DAC instead.
http://hifimediy.com/DACs/9018-dac Around a hundo for 384kHz/32bit max sampling/112.5dB @ 1kohm THD.
However, this is all on paper. I'm damned sure it'd work though. I've wanted to play with it for a while now- maybe I'll pull the trigger and order some bits to swap into Naomi's car. If it blows chunks I'd still end up with a little DAC to use with a phone/PC.
M.