I have had success with both SpectroCoin and UQUID. The only concerns I really have with these are minimal compared to other similar providers which do require identification or similar data which you might not want to provide to a fishy company. SpectroCoin in my opinion is not clear on the monthly fee and whether you actually have to pay it. They say you do but in my experience I have not had to. UQUID on the other hand is quite transparent but right now you can't get a new card or load your existing one because their contract with their card company is out now. Because of this, I see SpectroCoin as the only option at the moment, but switching isn't out of the question when/if UQUID get a new contract.