Sure, here is the Bitcoin Core Objective-C open source library for iOS.

Supported features include:

• Encoding/decoding addresses: P2PK, P2PKH, P2SH, WIF format (BTCAddress).
• Transaction building blocks: inputs, outputs, scripts (BTCTransaction, BTCScript).
• EC keys and signatures (BTCKey).
• High-level convenient and safe transaction builder (BTCTransactionBuilder).
• Parsing and composing bitcoin URLs and payment requests (BTCBitcoinURL).
• QR Code generator and scanner in a unified API (iOS only for now; BTCQRCode).
• BIP32, BIP44 hierarchical deterministic wallets (BTCKeychain).
• BIP39 implementation (BTCMnemonic).
• BIP70 implementation (BTCPaymentProtocol).
• Automatic Encrypted Wallet Backup scheme (BTCEncryptedBackup).

and more under development (pls see their roadmap section)

You can check here