I just visited http://www.oxid.it/ and foun out they now have a version of Cain for Pocket PC. You can download it here:
http://www.oxid.it/downloads/Cain_setup_PPC.ARM.exe
I don't have a PPC and more, could someone please test it out and let me know if it has the normal Cain's sniffing/ARP poisoning functions?

Here are the features they do list:

Cain for PocketPC (ARM) v1.1 released. Download it here.
Requirements:
- PocketPC 2003 device with an ARM based microprocessor architecture (eg: ipaq6515, Qtek 2020, Qtek 9090 ....).
- Microsoft Windows CE or Windows Mobile operating system.
- 5 Mb of free memory
Features:
- Rainbowcrack-online client (works with any Internet connection available such as GPRS, ActiveSync .... ).
- Dictionary Attacks for the following hash types: MD2, MD4, MD5, SHA1, RIPEMD160, CiscoPIX, MySQL v3.23, MySQL v3.23 + challange, MySQL SHA1, MySQL SHA1 + challange, LM, LM + challange, NTLM, NTLM + challange, NTLM Session Security.
- Hash Calculator.
- Base64 Password Decoder.
- Cisco Type-7 Password Decoder.
- Cisco VPN Client Password Decoder.
- VNC Password Decoder.
- Microsoft Messenger Password Decoder.