1. ThingSpeak : Thingspeak was the first service I used to connect my device with the Internet, so maybe that's why it's first in the list. Considering the ones I used later on, ThingSpeak had perhaps the easiest learning curve to get exactly what I wanted from a web service. To upload data, store it, see it, and read it from another place. It allows you to have different channels to read data from different sensors from the same device.
It utilizes a RESTful API like many of those on this list, which allows the user to GET and PUT data using the browser alone. With such an easy API, which can be used with curl on Linux based systems like the Raspberry Pi or Intel Edison, you'd imagine it to be pretty bare bones in terms of functionalities. You'd be wrong.
Thingspeak offers integrated MATLAB analysis on incoming data on the cloud, making it a powerful tool for analytics. Statistical analysis of your dataset is a breeze when you're integrated with something as powerful as the almighty MATLAB.
It also provides APIs to interact with Twitter. In addition, it has support for command queuing and automation with event triggers as well.
The only downside I saw in this platform is the messaging rate which is limited to 1 message per 15 seconds. This does hamper time sensitive systems as a delay of over 2 seconds is considerd huge in say robotic control. Although you can circumvent this by spreading control commands over a number of channels, that would require a more complex device side code in addition to security key complications.
2. Dweet.io : I discovered Dweet.io recently while searching for platforms providing lightweight communication between machines which allow a very low dead time. My intentions were to use it for a real-time system which responded to commands in a negligible amount of time, and Dweet.io almost gave me that.
First of all, it disposes off with the whole sign up and register system, and gives you direct access to your own data repository over a URL. Just entering your own unique device name in the URL provides a small chunk of cloud for you to experiment with.
Dweet also uses something called HAPI web API, which makes responses to Dweet requests understandable to humans rather than a convoluted output format. This makes grabbing required chunks of the response incredibly easy.
I haven't experimented with it yet, but it also lets a physical device subscribe to a Dweet stream. From my standpoint, the event driven action ensures low battery use, which is a good alternative to constant polling, much like the TCP messaging stack.
And finally, Dweet's USP is the transmission delays. As it does not have any heavy cloud machinery hungry for data in the back end, it is a mediator in the purest sense, which gives you blazing fast transmission delays. You can almost call it real time. A 1 message per second rate limit is impressive, to say the least. haven't seen it in many other places.
3. Temboo : Temboo is perhaps the most popular and versatile platforms available for free on the Internet, with a number of useful APIs spanning from Twitter and Facebook to Google Drive access and integration of Google analytics tools such as Google BI.
It's entire software stack is devoted to connecting existing web applications such as social networks and cloud storage to physical devices for interaction. Although their hardware support is limited to texas Instruments and Arduino platforms, their impressive list of SDKs more than makes up for it. You can implement your Temboo appication in your favorite language, and connect to a number of services through it
Temboo has a rather easy learning curve if you consider the possibilities it offers. Although i wouldn't recommend it to beginners, it is a great service to utilize if you are familiar with communication protocols, API design and have a good hands on with any other service.
This is actually a huge platform to explore, and a great one to rely on for integrating your IoT solution to your favorite web service.
4. Mediatek Cloud Sandbox : Mediatek labs opened its own proprietery Cloud Service called the Mediatek Cloud Sandbox, and although it's targetted mainly at the Linkit line of SoCs, the APIs are open to anyone who wants to experiment with cloud service integration into their project.
It is more POC oriented, so don't expect a fleet of advanced features to help in industry level deployment. That is actually a good thing, because that makes the Mediatek Cloud Sandbox a great place for beginners to start.
The Linkit line of SoCs prides itself on its low power consumption and good peripheral support. Therefor it is advertised as a a development solution for wearables as well as IoT. The Mediatek Cloud Sandbox reflects this fact by implementing a RESTful API over HTTP to facilitate power resourceful opertions.
As the Linkit SoCs come bundled with GPS based location sensors, the Mediatek Cloud Sandbox has the welcome addition of geo-location logging which can be useful to a number of applications which aim to combine machine learning with geo-sensing abilities.
With a comparatively simple setup, thorough documentation and a fairly easy learning curve, the Mediatek Cloud Sandbox is a great starting point for beginners to start from if they aim to stay with the same service throughout.