To be honest I wouldn't be happy putting my card into a phone or any portable device that's not within the companies location especially if it doesn't prodiuce a paper receipt for me.
From a company view point i don't want to wait 14 days for my money nor do i want to pay 2.75% on every transaction. I can't remember waht we pay now but iot's certainly well less than 2.75% and we only pay about 45p for debit cards. our bank account is credited within 48 hours for all our card payments (which must be over 80% of our business excluding invoice payments)
We've struggled with the 'Card Holder Not Present' for some time and with the change in banking regulations we can't now, just like you, accept emailed card details. We now have a direct computer access system which works through our Merchant Services provider and it works just as well as inserting a card into the standard terminal. We only take payments at the base so if we're off site and need to process a card we do a card holder not present transaction back at base.
Why not try to have someone abvailable to do the CHNP transaction for you back at base rather than this system which isn't, in my view, in your favour.