Not sure if this should be a deal because this isn't exactly available in Australia.
Singaporean telco StarHub offers two prepaid SIM cards which benefit from its ‘Happy Roaming’ package, where you can use the plan's initial data allowance of between 2GB and 5GB for free overseas roaming.
Here are the countries and networks covered by this deal:
- Australia (Telstra, Vodafone)
- New Zealand (2Degrees, TNZ)
- China (China Mobile)
- Philippines (Smart)
- Hong Kong (Three)
- South Korea (SK Telecom, Olleh KT)
- Indonesia (XL Axiata, Three, Indosat)
- Taiwan (FarEasTone, Chunghwa Telecom)
- Japan (NTT DoCoMo, KDDI)
- Thailand (TrueMove, DTAC)
- Macau (CTM Macau)
- UK (Three)
- Malaysia (All networks)
- USA (AT&T, T-Mobile)
So if you're travelling to these countries through Singapore, or meeting up with friends from Singapore, this is perfect for a holiday.
Thanks! Three UK also does this, with free roaming in 71 countries: http://www.three.co.uk/go-roam
One complication with it was that online top-ups required a UK credit/debit card, so you need to buy a top-up in person from a supermarket/newsagent.