Got to love the Spark.IO device, which I have been ignoring while I worked with the UNO and Netduino boards, mainly because the use of Wi-Fi, while cool is not really an option in large events.  And a large event is anything that jams the local Wi-Fi transceivers.  This jamming happens at most events, WiFi sense is awesome on your phone, but not so good if you are trying to get 30 or 40 people to do one thing.  Oh well.

UNO Shield Shield (more if you scroll down)

The Spark.IO is pretty neat, and they made some cool boards that you put your spark.io chip into, one is a UNO footprint board, with when bought with the Spark.IO is $59 US.  Strangely enough that is the “list” price sort of for an UNO device.  In fact, kind of wish that the Arduino did this with their Nano board so you could use UNO shields.  Also, note that the silk screening is clear and easy to read, like the Netduino.  USB provides power both to the Spark.IO chip and the UNO simulator board itself, or use the typical power plug.  See: https://www.spark.io/ , store.

Relay Shield

Got it but haven’t used it yet, looks good and the same configuration, one Spark.IO chip and away you go.  Let’s face it, the relays work or they don’t.

Same URL: https://www.spark.io/ , click store, for $30 US it is competitive with the Arduino and again the silk screen is clean and readable without my glasses, which I like.

Other Shields and stuff from Spark.IO (May need to scroll down)

Battery Shield, verdict: Weird shape, see what I mean?  Why this shape?

Spark Maker Kit:

Well thought out kit, you need nothing else to get you started, although the UNO simulator, as I call for $20 is a good addition. 

If you need sensors I would go with the SunFounder Kit from Amazon if you need it quick or DX.com if you can wait, there is quite a difference in price for the SunFounder kit.

Amazon Sunfounder sensor kit: http://www.amazon.com/SunFounder-modules-Arduino-Mega2560-Mega328/dp/B00CBDUD60/ref=pd_sim_sbs_pc_11?ie=UTF8&refRID=1CBZDCV1ZTHSC22E7QRK , cost $72.99 US

Dx.com: http://www.dx.com/p/arduno-37-in-1-sensor-module-kit-black-142834#.U589v6xOXIU cost: $44.99 US