I am wondering if any of the data logging multimeters could be adapted.
Uni-t, Brymen, Agilent have data cables via IR leds.
Text to speech using a computer, or if microcontroller w/ text to speech ic.
Might be easier to hunt down the talking ones mentioned before.
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It does have me thinking a device to read battery life might be more practical to more vision impaired people.
eg, a AA battery charger, that says the voltage or life or even beeps charge level. 1,2,3,4.
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In other news, Vision Australia have a
texpo in Melb & Sydney soon. I think is mostly android apps however.