The new Kestrel Elite Weather Meter with Applied Ballistics which has been referred to as the Kestrel 5700, is an updated version from the Discontinued Kestrel 4500 Applied Ballistics Meter in November of 2015. That being said... functionally, you're not getting more environmental or ballistic features. So don't feel the need to upgrade unless you find the other exciting changes necessary.
If you select the Bluetooth Kestrel LINK model, you'll want to download the Kestrel LiNK Ballistics app to your smart phone to load your guns / ammo to the meter. The new Kestrel Meters with Bluetooth include the software necessary to communicate wirelessly at a range of up to 100 feet with a clear line of site (walls or obstacles will effect this range).
There is a free app for both Andoird and iPhone for the Ballistic Profile Loader. This is what you use to load your Gun/Ammo combinations to the Kestrel. You can NOT load your gun profiles from the Dongle.
The Kestrel 5000 USB cable is an option. This is most common to use with multiple meters. Example being, you need 20 AB meters, and you want to save money by not purchasing the LINK meters. You could get 20 non LINK meters, with just 1 cable and load up all your meters with the Mac/PC version of the Profile Loader.
All 5000 series meters will have both a bright green backlight, which is great for even high sunlight conditions, and a night-vision preserving backlight. The red night vision (NV) backlight incorporates optical filter to reduce overall brightness and minimize blue and green spectrum light to preserve night vision. (Note: This 'night vision' is not compatible with night-vision equipment.) Basically, with the red backlight, your eyes don't need to adjust when looking from your meter to the horizon in night time use.
This Kestrel 5500 with Kestrel LINK will work in conjunction with compatible range finders like the new Bushnell Elite 1 Mile CONX range finder you've been reading about. It will also work with many other apps on the market for ballistics and weather functions. It's the most popular for ballistic applications due to the compass with crosswind functions.
The Kestrel applied ballistics meter combines sophisticated environmental sensing features with long-range shooting ballistics information in one hand-held device. The built in Applied Ballistics softwareprovides all of the following: