Twilio has been a dream for SMS implementation, though I don't think they are appropriate if you need SMS outside Canada / the US at the moment. Their customer service is quite nice, too.
Words cannot describe how crazy I think picking a platform based on $10 of costs for development is, by the way.
Thanks Patio. BTW, do you know who the blogger is who wrote the review? I'm curious to know his background, as this is the only post on his blog, and this is his only HN post. Seems a bit odd.
His name's David Wilkie (not betraying any confidence - he lists his name in those email threads he posted).
I don't know him personally, but he's been a regular in our IRC channel over the last couple of months. I believe he's a web developer living in Vietnam. Why do you ask?
Exactly right on the international thing. I tried a couple of things with Twilio and liked it a lot. But their SMS get rejected by most german carriers, which does not make it a viable option at the moment...
Never used it in anything with enough volume to care about a cent or two here and there, the API is excellent, and incoming messages work a treat too.
Related: I also like http://tringme.com/ for actual calls, although their documentation and support is terrific (or was when I checked), their service is pretty good once you understand how the hell to use it.
The cheapest small-traffic solution I've found is to hook one or more phones to a PC and communicate with them via Hayes AT commands. Can look a little hacky, but once you have the box set up, you don't have to worry anymore. Switching "gateways" is the same as switching sim cards.
I'm always a bit surprised this doesn't some up more often in these discussions. I used to use little serial GSM/GPRS modems anytime I needed to handle SMS, and that was while working for a voip company with lots of infrastructure in place for that kind of thing (the modems always won based on simplicity, speed, and consistency).
At the small scale spending $100 or so to have an unlimited test system seems comparable, and for large scale I'd much rather be buying a few unlimited SMS plans than paying per message. If the wireless provider supports SMS over GPRS you can do something like 30/min so you may never need more than one modem and sim. I wonder if it is just the barrier to entry, since you have to know that such a thing is possible and hunt down hardware/software to fit your needs rather than just buying in to one of these companies' pitches.
There's lots of do it yourself ways to do SMS. You can also grow all your own food, but grocery stores tend to be the more popular option.
Companies choose to work with an SMS provider because they don't want to have to solve uptime, scale, and service issues themselves.
When you're small, running your company on a web server under your desk connected to your cable modem probably works just fine. Doing the equivalent with SMS might make sense at that stage, too. As you grow, your needs change.
One thing to note is that in the US, "unlimited" plans aren't actually unlimited. Read the fine print on your contracts. Carriers define a limit to the number of messages they consider to be reasonable use. It's a soft limit, so they don't immediately block or ban you for going over once in a while. But if you do it consistently, they'll start to charge for the overage.
This is what I do -- I have one cheap GSM modem attached to an Ubuntu box, and I use stuff from the gsm-utils package to both send and receive messages. My problem is that I can't keep the system up 24x7; it's only active during working hours, five days a week.
You should try gammu, it has great documentation and support for modems. Using cell phones seems spotty on whether they will support sending or not, but I think that is independent of the software.
Has anyone used Tropo in a serious capacity? I'm currently using Twilio for SMS, but Tropo's integration with various IM services and very slightly cheaper SMS pricing may be compelling enough for me to switch.
I'm Tropo's product manager. We've got quite a few companies using Tropo in significant capacity. In fact, because of our ability to scale and telephony expertise (Tropo's a product from Voxeo, the largest worldwide voice application host), we regularly see customers switch from other providers to Tropo.
Words cannot describe how crazy I think picking a platform based on $10 of costs for development is, by the way.