Beeps and why they are usually bad ("Ecosystem of beeps" blog entry). Tone types. Audio readback best practices. Look at med reminder for some of these. Voice input. Vibrate is just crappy haptics. Include it.
Some notes and research I have gathered. Mention there's lots and lots around all this, and that much of it is for cockpits and so on. Places where there's noise, or distracted users. See Dark Cockpit (or something) principle for something else interesting. Anyway, make sure folks get referred to the various research. Please feel free to pick other references. I skimmed these, and am not happiest with them, just didn't want to pay $30 for each of several more important papers.
REFERENCE: http://www.jstor.org/pss/55320
REFERENCE: http://ftp.rta.nato.int/public//PubFullText/RTO/MP/RTO-MP-HFM-123///MP-HFM-123-24.pdf
REFERENCE: http://www.sigchi.org/chi96/proceedings/shortpap/Beaudoin-Lafon/Mbl_txt.htm?searchterm=tones
REFERENCE: http://www.acm.org/uist/archive/adjunct/2002/pdf/posters/p21-read.pdf?searchterm=Auditory+Warning
Fun reference, but maybe not a "reference" http://catless.ncl.ac.uk/Risks/26.35.html#subj15
Keep thinking that I'd like to put in a volume one, but really it's not that good of a pattern. There are several on-screen volume controls that vary widely, and they are generally at the OS level (so few people design them). So unless you think I should include it after reading the rest of the book, you might just make mention of it instead, in the intro, like this.