So far all I've done on this project is capture some initial thoughts and possible components. I'm transferring those (raw) notes here:

The idea is to build into a kite a system that measures various parameters and reports them to an Adafruit IO page using a cellular network.

Things to measure:

Temperature

Pressure

Humidity

GPS position

accelerometer data

compass orientation

Could we use the known physics of a kite (how it orients to wind direction) to determine wind direction? Could this be done off board (at the web site) using the data from the feed, to spare processing power on the kite?

Is there a way to measure wind speed? Drones estimate this by determining how much effort they need to expend to hover, presuming they are countering the wind. A kite can’t do that. Bridle tension could conceivably be available, but this depends on more than just wind. Maybe: see https://www.grc.nasa.gov/www/k-12/airplane/kitelift.html

Potential components:

Processor+comms

Option #1: Adafruit Feather 32u4 FONA PRODUCT ID: 3027 $44.95

Option #2: FLORA - Wearable electronic platform: Arduino-compatible - v3 PRODUCT ID: 659 $14.95

plus

Adafruit FONA - Mini Cellular GSM Breakout uFL Version PRODUCT ID: 1946 $39.95

Comms accessories

Slim Sticker-type GSM/Cellular Quad-Band Antenna - 3dBi uFL PRODUCT ID: 1991 $2.95

T-mobile 2G sim card

Sensors

Temperature/humidity/pressure (which can estimate altitude): Adafruit BME280 I2C or SPI Temperature Humidity Pressure Sensor PRODUCT ID: 2652 $19.95

Accelerometer/compass: FLORA Accelerometer/Compass Sensor - LSM303 - v1.0 PRODUCT ID: 1247 $14.95

GPS: Flora Wearable Ultimate GPS Module PRODUCT ID: 1059 $39.95