On a recent visit to Singapore and Sri Lanka I had the problem of how to get Internet and phone access. Gone are the days of having to pay a large deposit to have a local SIM card couriered for mobile access, or taking the hotel phone apart to connect a modem. It is possible to buy special travel SIMs. But as I make and receive few phone calls it was simpler to use the international roaming on Vodafone. Receiving or making a call while roaming can be expensive, but use of SMS is reasonable. There is the problem that each time you move more than a few km you can be on a different network which will send a "welcome to ..." message.
In Sri Lanka, I noticed Dialog was very common. As well as a mobile service (affiliated with Vodafone), Dialog also provide a CDMA service used for wireless home phones (common in guest houses) and solar powered public phones. For someone used to a wired infrastructure, it can be disconcerting picking up the phone in a hotel room and finding it is not plugged into anything.
On arriving in Sri Lanka, Dialog sent me a user id and password for their public WiFi hotspots with free credit. This service is common in guest houses and cafes. After using up all my credit I discovered that I just had to ask the guest house for their user id and password for free unlimited Internet access.
In contrast to the free Wifi in Sri Lankan guest houses,The Hotel Galadari in the Capital Colombo, charged $US7 a day for Internet access. This was available via Ethernet in rooms and WiFi in the public areas. But both the cable and wireless versions very slow (typically 40kbps).
While guest houses have free WiFi, getting it to work can be a problem. The service was not working in one location and when I asked about it the staff handed me the USB modem and router, suggesting I take it to my room and see if I could get it to work (I couldn't and suspect they had not paid the bill).
Singapore has very good free WiFi in the airport. Previously this required registration, but is now available without. Similarly many cafes have free wifi.