I think there needs to be an option to see the phonetic spelling of words as the robot can be very hard to understand in some cases.
That's a good idea, even though I've always found phonetics to be of little help. But that's just because I never bothered to study the phonetic alphabet (if that's what it's called) and respective sounds. Maybe if a guide is included, with examples in English e.g. Character x sounds like the "a" in the English "nightmare", and/or sound to exemplify, it could be a great addition to Duolingo. Of course, the priority should be improving the robot spelling. If implementing this would rob them of significant time for improving pronunciation, I don't think they should do it (in the near future; ideally, it would be a great tool for perfectionist in doubt of the robot).
It's a great idea to include a guide as not many people have studied any phonetic alphabet. I think the IPA (international phonetic alphabet) is a good choice as it covers all the sounds in the known human languages. I think that many of us here want to continue learning other languages, so it would be much better if we used the same symbols for all the languages. We would hear and see the differences between the sounds of the different languages. A comparison guide of sounds would be very nice!
I'm not sure that's accurate enough, especially applied to certain languages very different from English. Besides, sometimes there are sounds that simply don't exist in English. In that case, there's no accurate form of spelling it, you'll just get an approximation. Like the Spanish "ñ" and equivalent Portuguese "nh", for instance.
I'm taking the Dutch course, and the way the app reproduces the sound of the words is strange, I end up pronouncing everything distinctly... This option needs to be added, it would be of great help specially with these Scandinavian languages that have the same root as English (the writing is so different than the pronunciation), so when we see these phonemes we feel more comfortable and secure, that would improve inmediatly our pronunciation and even comprehension. The whole process would be greatly ameliorated.