I only just discovered this and it's so useful that I have to share it. I've had Photosmith on my iPad since before Lightroom mobile existed, but never got much use out of it because of the way the iPad restricts the camera connection kit to import all your RAW files, and strip their names (not to mention their SD card reader is limited to 32gb cards). That meant realistically I had to be at my computer anyway before importing first to Lightroom, and then sending JPEGs to the iPad for tagging, by which time I might as well have sorted through them on the big screen anyway.
Now, after getting an Eye-fi card and finding their own app a bit limiting, I realised I could use Photosmith to import small JPEG files directly from the camera in real time, and then sync any picks etc. later to my lightroom catalogue when I import the raw files on the computer (JPEGs stay on the iPad, only RAW files go on the computer).
The set-up is already covered in depth on the photosmith website here. I only found the guide and realised it's called a JPEG proxy workflow after setting it all up and thinking I'd done something clever.