Fitness Trackers/Tracking Exercise on MFP

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I've been working with a personal trainer for the past month as I restart my weight loss journey. At the end of the month, I'll be going solo so I'm looking at ways to stay on track. I'm toying with the idea of a FitBit because my best friend has lost over 3 stone this year with the "help" of her FitBit Charge.

However, my lifestyle and hers are different and I do a lot of gym work including weights and HIIT so I don't know if a fitness tracker would suit if I have to manually enter everything anyway. If I was to take the plunge, I'd be looking the price range of Charge. So I'd love some opinions on whether a fitness tracker would suit me personally - I've heard some really mixed reviews.

Speaking of manually entering exercises, as I've mentioned, I do HIIT and weights. An example of an HIIT circuit I do is: SkiErg – 30 secs, Med Ball slams x10, Kettlebell deadlifts x10 - rinse and repeat a lot. So how would I add this to MFP so I can track my exercise as well as my food?

Looking forward to reading your replies!