Can't say I've seen an auto3g app, I'd also like to know what it does.
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Auto3G is a jailbreak tweak which turns off the 3G radio when the iPad is in sleep mode, thus reducing battery drain (in theory). When you wake the device it turns it back on again. Hence Auto3G
The iPad2 can only be jailbroken on 4.3.3, so the answer is no. Apple do not allow official apps to have this type of control over the radios.