A number of iPhone audio accessories with the former 30pin dock connector have been discontinued lately because they won't work with the iPhone 5 and the newer iPad models. This goes for the Rode iXY stereo mic as well as the three Tascam products: the iXJ2 mentioned in this post and the two plug-in stereo mics iM2 and iM2X. Prices for these items have dropped considerably over the last weeks.
I've bought a iXJ2 and tried it with my OKM ear mics with and without their A3 preamp and the results are quite good. The iXJ2 really is a clever little device. With its two 1/8" jack sockets it can be used with one stereo mic or line source connected to either of the two sockets or two mono mics using both sockets. The interface has a built-in limiter which can be stereo-linked by a switch at the side and it supplies switchable plug-in power for electret mics like the OKM.
I've also got the iM2X stereo plug-in XY (well, sort of XY) mic and it sounds far better than one would expect at its price. Of course, it doesn't compete with 'real' condenser mics and a 'real' audio interface but it gets damn near. One should however not forget to switch off the GSM portion of the iPhone because it interferes with the recording. This is also mentioned in the manual.
While none of this stuff is professional-grade material, it can produce quite decent results if you know what you're doing. Much like a camera, the best audio recorder is the one you've got in your pocket when you need one...
And there's certainly no less conspicuous way to make a recording that with an iPhone and two earpads (OKM ear mics).
Here's a short recording of a rain shower in my back yard made this week with the iM2X stereo mic thingy at almost full sensitivity (8/10):
http://www.fotoralf.be/audio/hofregen.mp3Ralf