We are developing a wireless device (not a phone) that will need to transmit small amounts of data to an internet server. Although the packet sizes will be small they will be moderately frequent (sent every 10 seconds).

I'm wondering what network connectivity options I have as possibilities? We want to keep the price of the device under $100. Currently I've identified:

1. Wifi - Problem with this is not all locations the device will be in have wifi, so it will add to the cost of our customers.
2. GPRS - GSM data network - Not sure how much this would cost, because it would have to be associated with someones cell account right?

The device itself will not have a cellular component to it, unless it's cost effective and it gives us a cheap way to interact with the web. I'm assuming I can get a standalone GPRS module to make GPRS work.

So, do I have other options available for internet connectivity?