Technically yes but usually they are marketed purely as powertags such as this one: http://www.ebay.com/itm/Action-Replay-Datel-Amiibo-Power-Tag-PowerSaves-PowerTag-/172794255325 . thts just an example, have no association with that link neither have i brought from that seller so use your judgement.
PowerTag is a NFC tag but with the ability to write to any page even after it's locked (it has a secret key which let you reset it). PowerTag is not 100% identical to a legitimate NFC tag but so far atleast those differences are not checked for by Amiibo readers (might change in the future)...
There is a experimental feature in the latest version which let you use the "PowerTag" tags (which are meant to be used with powersaves) directly as a rewritable tag. They are reletively cheap so you might want to try that.
Yes the PowerTag key algorithm is not fully understood so we can only use predetermined key. I think we can still randomise it to 6 different UIDs but it wasn't as high priority.
The fact that a rewritable tag can be had for quite a cheap price meant I wanted to get this out even with the...
New version (2.6) has been released.
@AnalogMan , I've added support for PowerTags. I think you have one, think you could give it a test? https://github.com/HiddenRamblings/TagMo/wiki/PowerSaves-Support
HCE implementation does not allow generating a tag uid with 04 start byte. which is a requirement for the Amiibo emulation. This was discussed at large in the originial amiibo creation thread and other forums. It was rumoured that Nexus 5 running a very old version of CyanogenMod *might* have...
Can you patch D9 code so it would spit out the errorlevel reason so we can figure out which validation failure caused it to fail:
https://github.com/d0k3/Decrypt9WIP/blob/master/source/main.c#L91
I would do it but I don't have a build enviornment at the moment.
If it's just you being unsure about which console the backup belongs to: you can backup the other console and compare the new backup with what you have to figure out which console the backup belongs to. (It wont be an exact match but most of the binaries should be the same if its from your other...
It was mentioned in many places that some of the features don't work exactly the same between the two, and for one or two things Decrypt9 was more reliable.
I remember reading about how the wifi adapter inside the 3ds getting loose making it not boot in a similar way. Might want to open it up and reseat the wifi adapter: https://www.ifixit.com/Answers/View/304268/3ds+xl+powers+on+but+won%27t+boot