IP rating is IMHO critical. If people start relying on it to live their life, getting it killed by unpredicted rain or an accidental water splash will be quite a shock.
Battery life could be worked around if they're really that much of an improvement in day to day use. Even buying two or three pairs to go through a full day could be a worthy tradeoff if they don't need to pair to anything. Cost could be an issue, but 2 or 3 of them would still be cheaper that many hearing aids for instance.
