SINGAPORE - A 0.5mm thick sticker carrying a SIM card aims to offer consumers a cheaper way to stay connected when they are overseas.

Launched on Thursday (Sept 15), the product is the brainchild of two-year-old Singapore start-up Interfone, which promises up to 90 per cent cheaper roaming rates.

The sticker works with the firm's My Interfone app to allow users to download virtual prepaid SIM cards from participating countries.

In this way, users do not need to buy a physical prepaid SIM card in the destination country, or need to switch mobile number.

The sticker-cum-app solution, which took two years to develop, allows users to keep their existing local numbers while travelling.

"Not needing to switch out a physical SIM card, or change mobile number, will definitely be a draw to consumers," said Erik Rasmussen, chief executive officer of Interfone.

Its SIM sticker - which comes free with a $30 call and text credit purchase on its website - is meant to be stuck on the back of one's local SIM card.

Users must register the SIM card sticker via the My Interfone app before they travel. The same app allows users to top up their credits starting from $25.

Data roaming is available in 100 countries via global telco tie-ups. In the United States, Interfone works with AT&T. In Hong Kong, it is with CSL and Hong Kong Telecoms. In Malaysia, Interfone has partnered Celcom and Maxis. Its Singapore partner is Singtel.

Interfone also promises cheaper rates of up to 90 per cent in destinations like the US and Britain.

For instance, calls made or received in Malaysia, Australia, the US and Hong Kong cost 49 Singapore cents a minute using Interfone's solution.

Traditionally, calls cost at least $4 per minute to make - or at least $1.50 per minute to receive - while roaming in these destinations.

Each SMS is at a flat rate of 29 Singapore cents using Interfone's solution, as opposed to 90 cents in the United States or $1 in Australia.