The chip in the ball is a no brainer. The technology is there and I don't believe the cost is out of the means of the NFL.
Replay for penalties should be implemented but not as coaches challenges. There are too many penalties called to ask the coaches to give up time outs to review penalties. When a penalty is called there is always a time out. The refs usually discuss the penalty and the spot of the ball which gives the replay booth people a chance to review the play. I don't expect many reversals of penalties but we all see the ones they call that are pretty bad. Maybe they reverse one or two a game. It is still better than what we see now. I don't think this works for penalties not called though. Here I would go with the idea someone else posted. If a replay for a TD, fumble, INT or other call is used and the refs see an obnvious penalty, like PI, facemask, etc. then the penalty should be called. This would help get call right, it might also cause coaches to refrain from unnecessary replays.
Replay should also be used for illegal formation calls, encroachment, offsides and false start penalties. So amny times you see a defensive lineman get a good jump and the refs call it offsides, but the replay shows he did not enter the neurtral zone beofre the ball was snapped. Replay could fix these calls. Other times we see OTs move early and it is not called. I have no idea why refs decided to stop calling these false starts but you see it a lot now around the league. Lane Johnson does it several times per game and rarely if ever gets called. The Eagles OL is successful on that Tush Push because they are really quick at the snap. It is a huge advantage to an offensive linement to get out of his stance before teh DL can get his hands on him.
The problem in the NFL is probably as much penalties that are not called as much as penalties that are called.
I also think they need to go back to the rules and call penalties according to the rules - or change the rules. For example, an uncatchable ball should negate any PI called. You rarely see the ref signal an uncatchable ball anymore.
For illegal contact, call it every time or change the rule to allow it. We complain about the refs because one play we see a receiver get mugged downfield, and the next play we see minor incidental contact 6 yards beyond the LOS called.
Hands to the face is either allowed or not allowed. It is called sometimes, but a lot of times you see it and the refs let it go. Holding is another one. Everyone grabs the sholderpads when they block and it they stay squared it is not called, but then if the guy being blocked turns and the blocker does not let go immediately, the refs call holding - sometimes. Other times they ignore it. Consistency would go a long way to calming everyone's concerns about penalties.
Finally, it is the refs. full time refs that get together and work on penalties calls, review videos, and get instruction in practical labs would improve the officiating. But they are still humans so they will made big mistakes. Major league baseball umpires are full time and they made some ball calls too.