You can use liquid ammonia drops (never heard of tablets), but you must be absolutely sure it's pure ammonia..... no other additives or detergents can be present. I've never used it, but I've heard you can find it at Ace Hardware stores.
If you're using drops, you have to monitor your ammonia level pretty much daily to make sure you're not adding too much, which can hamper the cycle. Then, once your ammo level starts dropping, you have to worry about continual dosing to feed the developing cycle. With the raw shrimp method, it's "drop it in & let it go".... Not as gross as it sounds, and it's very easy.
Wanna calculate the cost of that new reef tank?? Take your worst nightmare, double it, and you're halfway there.