Impact is an excellent option for data recording. I know the owner, graduated Scout Sniper School with him and was in the same platoon later on. He knows data recording, what is necessary and what isn't, and developed an excellent product that works on the firing line as much as data analysis post firing.
The best start is to get one of their complete books in the shooting discipline you're interested in and learn how to start using it. They're worth it for the additional pages included detailing wind calls, ranging, etc as well. If you're not sure what type of shooting you're going to focus on, get the premade or Sniper's Hide version to get the ball rolling. You can always add pages later but I recommend ordering additional pages if you know the types of targets you prefer to shoot.
As for digital, there's some options out there in conjunction with ballistic programs that are especially helpful in documenting shot group sizes on my phone, but more often than not I prefer old style pencil and paper for the general shooting session. I really recommend the Rite in Rain type and a good mechanical pencil for fine markings no matter the weather. The phone is just too small for ease of use behind the gun other than basic ballistic computer use, and I'm not savvy on bringing the iPad to the firing line.