If connecting a smart device can create substantial customer value and you do not do it, your competitors will. Terry Ess provides a checklist of questions to consider and methods to evaluate. How much code is necessary for different options is covered in detail as well as the business case.
Given the high variance in characteristics, it is unrealistic to think that there is one single best solution. All of the solutions investigated can be implemented even on devices with fairly modest platforms. However, some key points can be made:
Unless you absolutely cannot afford the inefficiency, XML is the way to go for data format.
A basic profile compliant web service server is extremely attractive if you will need to tie in to a customer’s or you own IT organization and have a persistent connection. This option requires that you know what you are doing (both technically and otherwise). If “connecting” is new for your industry, approach this carefully. If your device works on the factory floor, you should seriously consider an OPC XML data access compliant web service.
If synchronous operation is not required for the connection enabled applications you will support, the email client is the safest and easiest path. It is especially attractive in circumstances where there is no persistent connection and you are enhancing a legacy device using an dial out version of an Internet chip set. It can be implemented, even on a large scale, without any need for extensive enterprise infrastructure using any of the widespread access ISPs.