The only realistic way to reach Nusa Lembongan from Bali only 30 minutes by boat. There are several options according to budget and speed. Come directly to Sanur beach and buy ticket to Lembongan island with fast boat or book your ticket online here (pick up service include)
Only one small hospital or Puskesmar (Community Health Centre) in Jungutbatu village. If there are severe injuries, the patient need to go to Bali for better health treatment. Travel insurance is a must.
Only 1 ATM machine available in the island. You can withdraw your money with Visa or Mastercard. Since only 1 ATM machine provide sometime the machine was out of cash. Bring enough cash will be great, some hotel & restaurant now already accept credit card payment.
Money changer also you can find around the island but the currency might be not good as in Bali