NOTE: this was tested on Pre3, but Pre2 should be the same
You can record phone conversation without need for mixing 2 sources ... you can record both mic and speaker at same time ... there are no technical issues (except jail, so official app in HP App Catalog is not possible) ... piece of cake - except day has only 24hours
For those with free time and required skills: don't use pulse audio, but alsa directly, for example try running this command while on call (will record 20secs):
then play back with:
arecord -D hw:0,0 -f S16_LE -d 20 /media/internal/rec.bin
Hope that helps...
aplay -f S16_LE /media/internal/rec.bin