Now that TextMarks has closed down the 'Lite' version of their SMS gateway service does anyone know of a suitable replacement? I've been primarily using them for their web gateway to allow me to talk to my home web server via SMS.
Currently I'm working on interfacing my server via PHP script, a Teensy (a baby Arduino clone) and a relay board to my Christmas lights and I would love to be able to allow me or anyone else driving by to control my lights by sending a SMS message.
I've looked around but I can hardly find a pay service like them let alone a free one. Plus, while a shared shortcode (like TextMark's) would be great, a full number would be ok.
Disclaimer, I do developer evangelism part time at Nexmo.
If you're only using a single cell phone, you may be able to put something together using your carriers SMS to email gateway (if your carrier supports that). Something like SendGrid would then act as a gateway, turning the incomming emails (your carrier acting as the SMS to email gateway) into requests on your webserver. As long as you can keep traffic to the free tier on SendGrid, there would be no cost.
Of course if you're only doing a small volume of messages, the paid SMS APIs might not cost that much. Here's a few APIs:
You'd pay something like a dollar a month for a virtual number (no shared shortcode), then per message (all depends on your carrier/country/API). The per message cost shouldn't be much (with Nexmo in the US it's less than a cent).
Also, if you're doing a lot of inbound SMS, it's worth noting that Nexmo allows unlimited incoming messages with the virtual number.
TextMarks did close the 'lite' (free ad-based) service to new registrations about a year ago, but old accounts were grandfathered in. So if you still have active non-expired keywords (sounds like you might), you can continue to use them and possibly repurpose them for your new app. However if keywords go inactive for ~30 days, they may get deleted permanently.
All the SMS API information is available here: http://www.TextMarks.com/api/
And the specific page for allowing people to send text messages to your application (which show up as HTTP requests to your app) is here: http://www.TextMarks.com/api/sms-auto-response/
P.S. the new subscription plans start at $19/mo, have no long term commitments, and there are frequently specials and coupons listed on http://www.TextMarks.com/front/specials/ Your app sounds cool! Best of luck, and hope you find something that works for you!
[Disclosure: I built a large portion of the TextMarks API! Ask me anything.]
You should write me an API for gtalk/Google Voice and then you can get exactly what you want. Problem is I don't think there are any prewritten APIs for that.