I've seen numerous posts around the interwebs about whether Flytrex works with T-Mobile. It does. And they will also allow you to use the 200MB/month for life plan with the device... which, for a 1 time charge of $10, basically gives you free Flytrex usage forever (unless you fly 8 hours/day for 30 days). Here's how I did it: 1) Go to a T-Mobile store and buy a pre-paid GSM sim card. Make sure you specify data, not just voice. Not sure if this matters, but better to be safe. 2) Go home. Don't even try to get the salesperson to activate it for you. Nobody really knows of the 200MB for life plan, and they'll need the Flytrex IMEI, which wont work (more on this later). Then they'll try to sell you a 1GB/month plan for $30/month, which is way overkill. 3) Call the activation number on the SIM when you get home and tell them you'd like to activate a SIM card for a BYOD pre-paid plan, they'll ask you which plan and tell them "200MB/month for life". If the rep doesn't know what you're talking about, tell him or her to look again, it exists. 4) Once they find the plan, they will ask for the IMEI of the device you're going to be using. Give it to them (it's in your Flytrex account settings, click the Live link, click Manage next to the device youre trying to register, its on the bottom of the page). 5) At this point, they will tell you that the IMEI you provided is for a cell phone and it won't work. The 200MB for life plan is meant for tablets, so just ensure them that it isn't a cellphone. I told them I was working on a hobby project that requires a GSM data connection. 6) If they push back, just make up what the hobby project actually is, or tell them what the Flytrex does, and that it will use far less than 200MB/month. Make sure you mention that there is no way to interact with the device, because they may want you to log onto the T-Mobile activation website from the device. 7) If all goes well (and it should), they will just plug in a dummy IMEI number for the Flytrex associated with the SIM card. I confirmed this by logging into the T-Mobile website and checking my account details. The IMEI is definitely not the one I gave them over the phone for the Flytrex. 8) That's it. They said it can take up to 2 hours for activation, but my Flytrex LED went from purple to blue to blinking green while I was still on the phone confirming that I got the plan I was originally requesting. A couple of other things: They will ask you if you want to add a credit card to the account. I assume it's to add credits to the account if you go over 200MB. Since I don't plan to, I didn't. I also didn't trust that I was signed up for the correct plan and didn't want to get charged if that were the case. I recommend not adding a card just in case. You can always add one to the account after the SIM is active and you can confirm the plan is the right one. I may end up adding one now, because it would suck to go over 200MB for some reason, then have a fly away and not have the Flytrex transmitting because you're over your data allowance. Write down the phone number they generate for the SIM!! You will need it to log into the T-Mobile site and look at your account details and confirm you got the right plan, add credits, etc. The 200MB/month plan is meant to be tied to 1 particular device. However, (and I have yet to confirm this but will when I get another Flytrex in 2 weeks) since they put in a dummy IMEI, the network will never know whether you put the SIM in another device, so I assume you can use the same SIM with multiple Flytrex's and essentially share the 200MB. Hope this helps.