Wireless communication from iPhone to arduino

I want to use my iPhone to send a message wirelessly to an arduino. I guess I could use BLE or wireless. I want to do this out and about so I won’t have a wireless router.

I’m pretty familiar with C/C++ but not java or anything like it. I’d like to use Sparkfun gear if possible, any suggestions on the easiest and cheapest way to achieve this?

Gareth

Use a static IP on the Arduino that’s known to the iPhone?

A lot of people use Bluetooth.

Writing code for classic Bluetooth on iPhone requires that you are a member of the Apple Developer Program. BLE doesn’t.

Narrow down “Out and about” please! Middle of nowhere? Distance to Arduino? Internet acces? Open wifi router in the vicinity? Cell phone coverage?

I’ll be close to the Arduino with my cell phone. (10 feet or less). I’m assuming cell phone coverage as I am in the USA. I would not think it was safe to assume ao open wifi connection as this is a mobile (in vehicle) application.